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The effect of dryness on the skin
ELSEVIER
The EfSect DONALD
RUDIKOFF,
of Dryness
on the Skin
MD
after she had bathed him and anointed him with oil forth from the bath he came, in bearing like the immortals Homer, Tlze Odyssey1 . water giveth and water taketh away .
Shelley and Shelley2 ractitioners of medicine have recognized the importance of water for human life since time imP memorial; yet, until quite recently, there has been scant mention in the literature about the effects of water loss on the skin, and it is likely that dryness of the skin is, for the most part, a modern phenomenon. A thorough review of the subject in 1972, led one clinical investigator to conclude, ‘I. . . man-made environment has become the most common cause of an increasing incidence of dry skin and of the variety of cutaneous conditions resulting from this. Cleansing agents . . . and rapid changes of temperature and humidity universally encountered either in overheating or air conditioning in homes, offices, airliners, and automobiles are among the modern, everyday environmental factors that contribute to the almost universal occurrence of dry skin of people living in the cities and the suburbs . . . .“g During the last 25 years great strides have been made in understanding the mechanisms by which the integument retains moisture and regulates the body’s “aquatic milieu”; however, dry skin remains one of the most common and vexing human disorders. Ubiquitous advertisements for moisturizers and the profusion of skin-care books attest to the magnitude of the problem. This paper will examine the historical, clinical, and pathophysiologic aspects of dry skin and related dermatoses, as well as the impact of dry atmospheric conditions on the skin.
Definition The term xerosis or “dry skin” is used interchangeably by physicians, patients, and the cosmetic industry to describe a dermatosis with features of roughness, flaking, scaling, fissuring and apparent lack of moisture.4,” The condition is frequently associated with an atopic state and varying degrees of ichthyosis vulgaris. There -.____
.__--
From the DepartmerIt of Dermatology, Mount Sinai Medical Center. New York, Nezu York. Address correspondence to Donald Rudikoff, M.D., Box 1048, The Momf Sinc7i Medical Center, One Gustave L. Levy Place, New York, N1 10029-6574.
0 1998 by EfsezTier Science Inc. 655 Az~enur of the Americas, Neul York,
NY 10020
is no uniformly reproducible definition for xerosis, and a number of terms based on symptomatology, physical signs, and presumed etiology are used synonymously by clinicians.6 These include xerosis, xeroderma, asteatosis, asteatotic dermatitis, winter itch, rough skin and chapping. This terminology, to a Iarge extent, reflects the misapprehension of early practitioners who speculated that dry skin was caused by an absolute or relative deficiency of sebaceous secretions.7,8Another term, reserved for severely inflamed and dry skin resembling cracked porcelain, eczema craquele, has aptly been described as “a rare form of eczema . . . in which a reddened surface is covered with large, thin flakes or scales, separated and outlined in polygonal areas by superficial cracks or fissures.“8 The dry appearance of skin is now generally accepted to be a consequence of the scattering and reflection of light off a rough surface that results from abnormal desquamation. In reality, not all skin that appears or feels dry is actually dry.“rY Consider the dry itchy skin of both chronic renal failure and old age, which typically have a normal moisture content.iOJ1 For accuracy, an investigator recommends specifying the following qualities when describing xerosis: (1) rough versus smooth; (2) seborrheic versus asteatotic; and (3) dry versus hydrated.6
History Early authors recognized the occurrence of dry pruritic skin under winter conditions. While exploring the history of “Dermatitis Hiemalis,” a group of investigators traced the expression “winter itch” to a seminal publication by LA Duhring published in 1874.12,‘”Duhring ascribed a “neurosis” of the skin to symptoms of pruritus, smarting, tingling, and burning that appeared in the fall, about the time of the first frost. The symptoms were of sudden onset, increased in the evening, and were exacerbated by heated rooms and hot stoves. Physical findings were minimal at first, with only dry appearing skin. Subsequently, the skin might become “rough and harsh”, displaying “redness, inflammation, and irritated hair follicles, with many hairs broken off short” . . . The usual sites of involvement were the extremities, especially the calves. Another investigator termed the condition “winter prurigo,” and at least one author mistakenly attributed it to constipation.i4J5 Variations in temperature were thought by some authors to be as important as frosty air alone.lh In 1891, an investigator described a dermatitis with a 0738-081X/98/$19.00 PI1 SO738-081Xf97)00173-9
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predilection for the dorsa of the hands and feet that related to low temperature, low humidity, and wind during the cold winters of Cleveland, Ohio.17 Travel to a warmer climate provided relief. In 1912, this investigator and his colleague answered criticisms that the etiological factor might be a dermatophyte by citing the lack of such organisms on pathological examination and observing that the condition occurred more frequently in the winter months when tinea was less common.18 Subsequent reports further validated the concept of a xerotic skin disorder with a seasonal predilection.19JO Travel from the tropics to a cooler, dryer climate was also implicated as a cause of dry skin in soldiers and civilians’i Decades later, while seeking a more quantitative explanation for the phenomenon of “winter itch,” a group of investigators related chapping of the skin to dry air as measured by dew point (ie, the temperature at which the moisture in the air begins to condense into visible form).22 They emphasized that symptoms of chapping were often preceded by moist air conditions, followed by a sudden drop in air moisture; and they noted that cooler ambient air, with a low moisture content, tended to be dried even further by indoor heating. In 1962, an investigator reported a pruritic skin condition identical to dermatitis hiemalis occurring during the summer months in Texas.23The condition resulted from long periods of exposure to air conditioning alternating with short exposures to a hot, humid environment. Paralleling the clinical recognition of dry skin conditions and their relationship to weather, travel, and environmental manipulations, the late 20th century has been marked by advances in our understanding of epidermal structure, skin hydration, permeability, and barrier function.
Physiology of Skin Barrier Function
Hydration
and
The skin is a complex structure that affords protection from the external environment. The major barrier to water loss from the body resides in the outermost portion of the skin, the stratum corneum (SC). It has been suggested that the main purpose of the epidermis is to generate this tough protective layer.z4 The SC is heterogeneous in structure, and it has been likened to a brick wall in which the noncontinuous, mostly proteinaceous, component, the corneocytes (bricks), are embedded in a continuous matrix of intercellular lipid (mortar).2s The SC consists of about 15 layers of flat corneocytes that are devoid of intercellular organelles and cytoplasm. They consist mostly of a core of bundled keratin filaments surrounded by a rigid cornified envelope.26 Filaggrin, a histidine-rich protein formed from the
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short-lived precursor protein profilaggrin, is the other major protein of the horny cells. Although it aggregates keratin fibers in vitro, this may not be the case in vivo.27 It is hydrolyzed further to amino acids and other compounds that are collectively known as natural moisturizing factors (NMF), with plasticizing, moisture-retaining and ultraviolet protective characteristics.2*,*9 The individual corneocytes have overlapping edges, and they are bound by corneodesmosomes whose disintegration is linked with desquamation.*5JO They may vary in size, depending on age, anatomic location, and upon conditions that influence epidermal proliferation, such as UV radiation.2” When there is an increase in the epidermal turnover rate, there may be a disruption of the orderly stacking. The result is a loss of barrier function.30 The SC thus serves as a barrier to evaporative water loss, and it also contains moisture within its substance.
Barrier
Function
of the Stratum
Corneum
Water reaches the skin surface via the eccrine sweat and by diffusion through the epidermis, limited only by the low permeability of the SC.31 The approximate transepidermal water loss (TEWL) of an average adult ranges from 85 to 170 ml per day. At rest, with no visible perspiration, the loss from eccrine sweat glands is about 300 to 500 ml per day, much of which is from the palms and soles.a’ Under very hot conditions, as much as 2 liters per hour may be lost as sweat.32 The TEWL from diffusion through the epidermis varies from 0.2-0.6 mg/cm*,/h, and it may vary in different parts of the body.“a-35 It is well-known that hydration dramatically increases the permeability of the skin;31 in addition, increases in skin temperature can increase the TEWL independent of sweating.“6 Water diffusion through the SC is by passive diffusion, a function of water-vapor gradient determined by ambient conditions.31 There is no evidence of active transport of water through the horny layer, and the contribution of the cutaneous appendages to the TEWL is minimal, owing to their small total cross-sectional area relative to the entire skin surface.37 Prior to the 20th century, the skin was considered impermeable, except possibly to gases.37By the beginning of this century, the skin was accepted to be relatively impermeable to water and electrolytes and somewhat permeable to lipid-soluble substances. The barrier to diffusion in the skin, once considered to be in the stratum lucidum, is now thought to be located in the SC throughout most of its thickness, and not just a small layer at its base.37-39 The suppleness of the skin once attributed to its fat content, was established by an investigator to be a function of the moisture it contains”0 This researcher
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postulated the existence of water soluble, “mucoid or mucoprotein” substances responsible for the water binding properties of the horny layer. Later termed “natural moisturizing factors” (NMF), these could be extracted with water from the SC only after solvent extraction of the lipids.41,42 The intercellular layer of the SC ranges in thickness from 0.3 nm to 20.6 nm, and it is filled with a nonhomogeneous material and lipid derived from the lamellar bodies formed in the spinous and granular layers.?5J” They expel their contents, including lipid, polysaccharides, and hydrolytic enzymes into the intercellular space, increasing the net intercellular volume and decreasing the volume within the cells. During the process of epidermal differentiation, there is a significant change in the composition of epidermal lipids, with an increase in fatty acids and ceramides and marked decrease in phospholipids.4” Simple glycosphingolipids, cholesterol sulfate, free sterols, and sterol esters are also found. The lipid composition of the skin may vary with age, sex, body site, and season.45-4”It is noteworthy that in some patients, during the winter months, there is a decreased proportion of ceramides, cholesterol, and fatty acids, with its implication for winter xerosis; though in young adults, ceramide mass remains relatively stable at various skin locations, even with change of season.45,48,49 There is good evidence, mostly from studies of epidermal permeability after solvent extraction of SC lipids, that these molecules are crucial for the barrier function in the skin and are probably more important than the actual thickness of the SC.44,50-52 Structural lipids, especially ceramide in the intercellular spaces, play a critical role in the water-holding properties of the SC.-5?Unlike the typical bilayer configuration seen in membranes, the lipid portion of the intercellular lamellae often consists of several alternating bilayers and monolayers?
Hydration Moisturizing
of the SC and Natural Factors
The state of hydration of the SC is governed by three factors: (1) water that reaches it from below, either from sweating or transepidermal transport; (2) water lost from the surface by evaporation; and (3) the ability of the horny layer to hold moisture.31 In addition, because of its contiguity with the underlying epidermis, the water content in the lower horny layer must be higher than at the surface, and, in fact, a gradient exists within the SC.37It is well-known that the ever changing ambient relative humidity can influence the hydration and water flux across the SC in a complex manner as determined by Fick’s law.55 Thus, the degree of hydration is never constant; and as long as the relative humidity is less than IOO%, there will be a net outward diffusion of
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water from the lower layers of the epidermis.x7 A group of investigators using magnetic resonance imaging (MRI) delineated two distinct areas within the SC of heel skin: an outer layer, where water content could be modified by external mechanisms, and an inner layer not altered by such manipulations.56 The midlayer of the SC has the highest content of extractable amino acids and the greatest water holding capacity.57,58 A number of different methods to assessthe water content of skin have been developed. These include analysis of water flux, electrical measurements (resistance, capacitance and impedance), heat conductivity, photoacoustic spectroscopy, viscoelastic properties, microwave propagation, dye fluorescence, topography, infrared spectroscopy, near-infrared reflectance spectroscopy, electron-probe analysis, and nuclear magnetic resonance imaging.55,56,59 The three species of water identified in the SC are: (1) tightly bound primary water of hydration bonded to polar sites on SC proteins; (2) secondary water, probably hydrogen-bonded, less tightly, to primary water of hydration, which increases in amount up to about 40% total water content, and (3) bulk liquid water, which does not appear until about 40 percent total water content is reached.6” It is the secondary water that is most dependent on the presence of natural moisturizing factors (NMF) and is most sensitive to changes in ambient humidity. The skin contains hydrophilic nitrogenous compounds that enable it, in part, to hold moisture.42 Extraction of these compounds results in a markedly diminished capacity for water retention. These natural moisturizing factors that make up as much as 10% of the dry weight of SC cells consist of a mixture of amino acids or their derivatives, including urea, urocanic acid, and, most importantly, 2-pyrrolidone-5-carboxylic acid.4y The latter constitutes about 2% of the dry weight of the SC, yet is virtually absent from other tissues and organs of the body .29,42,61 The natural moisturizing factors are derived from the breakdown of filaggrin as cells reach the SC. This breakdown is timed precisely and elegantly to the stage just after the permeability barrier is being formed.ay
Physiology
of Dry Skin
Much work has been done to delineate the physiological characteristics of xerotic skin. What we call dry skin may just be scaly skin. 62In a study of facial dry skin, conductance, a measure of hydration, and extensibility decreased with increasing skin dryness.e? This suggested that winter dry skin may result either in a drier or thicker SC. Severity of dry skin was associated with a decreased size of exfoliated keratinocytes. Patients with senile pruritus have also been shown to have increased intracorneal cohesion and altered skin surface
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contour parameters, suggesting an acquired abnormality of keratinization. The SC may become thicker and more hyperkeratotic if desquamation is abnormal. The SC cells may be shed together in large scalesrather than individually.25 In healthy skin, as keratinization progresses, desmosomes tend to be degraded. Thus allowing detachment and shedding of corneocytes. This is reflected in decreased levels of desmoglein-I in the outer stratum corneum. In a study of dry skin, the normal degradation of desmosomes did not occur, and desmoglein I levels remained high;@ moreover, desmosomal degradation is humidity-dependent, and it is reduced if the relative humidity is low.65 A good deal of work has been done on the actual water content of dry appearing skin using a variety of methods. A decrease in hydration and of extractable amino acid content of the SC has been demonstrated in dry skin of elderly patients, even though water content of whole skin including dermis is normal in these patients.66,h7Xerosis does not seem to alter the amino acid content in younger subjects.68 Certainly it is far from clear that water content is decreased in all so-called dry skin conditions, although this does seem to be the case in the dry appearing skin of atopic dermatitis and psoriasishy Because SC lipids are so important for epidermal barrier function, it would seem reasonable to expect that there might be an alteration of these lipids in xerosis. There does seem to be a decrease in SC lipids with age, but not with xerosis and asteatotic eczema.70-72Transepidermal water loss does not seem to be increased with age as might be expected, and it actually decreases;73however, aged skin may be more sensitive to environmental insults and recover more slowly than the skin of younger individuals.67 The relative importance of sebum-derived lipids toward the etiology of dry skin is controversial. They probably do not affect the moisture content of the skin to any great extent, but they may influence skin surface texture.74 A group of investigators consider decreased hydration of the skin surface in aged skin to be the result of a decrease in surface lipids due to reduced sebum secretion as well as a decrease in NMF due to poorly developed keratohyaline granules.75 Another group found decreased sebum production in older patients, but skin hydration was normal except in those who were immobilized.7h
Clinical
Presentation
The dermatologist is likely to encounter xerosis in a number of clinical settings. During the winter, especially in locales with low humidity, the relative humidity will drop indoors as a result of heating already dry air. Earlier in this century, with the advent of steam
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heat, a pot of water on the radiator became the poor person’s humidifier. Dry environmental conditions may be encountered in the home, on the job, on public and private conveyances, and in other situations. The patient may be older, with scrupulous hygiene, and may over-bathe. Elderly patients frequently continue the bathing habits of youth, with resultant dehydration of the skin. Dry skin conditions have been described in hospital wards, and in work environments where the humidity is kept low.77 A group of investigators described an occupational dermatosis occurring in workers at a telephone exchange installation, where the relative humidity was maintained at about 35% to protect metal contacts on electrical equipment.78 Similar circumstances have been described in factories that manufacture silicon chips and soft contact lenses, and they may occur in offices, in airplanes among flight crews, and high-altitude pilots.78-80 The dryness of the air in commercial aircraft is wellknown, with relative humidities in the range of 1217%.81,82The reason for this is that air at high altitudes has a low water content, and aircraft engineering constraints limit on-board humidification systems. Dry skin conditions may also be seen among hotel workers and traveling salesmen, as well as truck drivers exposed to dry air from heaters; and dry skin has been reported as a significant problem in the military.83 Dry skin and eczema are often encountered in the fishprocessing industry. 84Chapping of the skin and water loss from working in a hot or cold, dry environment can predispose the skin to penetration by some chemical irritants, resulting in irritant contact dermatitis.83 An investigator reported that xerosis seems to be a form of irritant contact dermatitis, the irritants being adverse atmospheric conditions, friction, and exposure to soap and water.3 Dry, irritated skin may be more susceptible to allergic contact allergens; and there is evidence that perturbations of the skin-barrier function may induce a greater concentration of Langerhans cells.85 Initially, dry skin may present merely as pruritus that is paroxysmal, exacerbated by woolen clothing and worse at night, when the patient is not as involved with the activities of daily life. 13In the elderly there may be disabling, unrelenting itch with minimal physical signs.9 Facial pruritus has been reported in the setting of low humidity in the workplace, especially if local heat sources are present.78 Conditions of increased air movement, such as high winds and exposure to unhumidified air from vents may exacerbate dry skin. 9 As previously noted, although such conditions are more prevalent during the winter, similar changes have been described in hot climates with air conditioning.2” This effect is enhanced by prior wetting of normal skin, particularly in individuals prone to xerosis. In addition, hot, dry and windy
Clinics in Dermatology
Figure 1.
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Xerotic skin with grayish-white,
THE EFFECT OF DRYNESS ON THE SKIN
cobweb-like accentuation
conditions encountered in desert climates can cause dryness and failure of sweat glands.86 The clinical manifestations of dry skin range from a rough, dry appearance to erythema, scaling, and excoriation. The earliest changes typically consist of a subtle, dull grayish-white, cobweb-like accentuation of normal skin furrows (Fig 1).23Individuals with darker skin may complain of a surface ashiness; moreover, the skin surface is likely to appear rough and uneven. With progressive dryness, tiny cracks (chaps or fissures) may develop in a retiform pattern resembling cracked china, with slight elevation of the free edges of the scales (Fig 2). With abnormal desquamation and irritation, fullblown eczema craquele may develop, much like cracks in dry mud.4 These polygonal “shrinkage cracks,” also seen in rock, concrete, and paint, are well-known to geologists and engineers. 87 An investigator has described painful hemorrhagic fissures of the skin on the legs of elderly patients with xerosis, eczema craquele, and underlying edema.87 If there is a pre-existing dermatosis, such as ichthyosis vulgaris or atopic dermatitis, there may be an exacerbation of the underlying condition. Many patients will have scaly skin on the anterior and lateral surface of the legs, with linear scratch marks, dried up blood, and hairs broken off close to the follicular orifices.13Similar changes may also occur to a lesser degree on the upper extremities, as may chapping and fine scaling of the inner thighs and flanks. Redness and
of normal skin furrows
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as well as pair@1 fissuring.
chapping is common on the dorsa of the hands, especially in the setting of frequent hand washing, as encountered among health-care professionals and restaurant workers. Painful fissuring, sometimes hemorrhagic in nature, may develop on the fingertips near the lateral nail margins (Fig 1). Workers with “low humidity dermatoses” have been noted to have pruritus and urticarial whealing as a result of scratching. This occurs mostly on the covered parts of the body. 78 Erythema, edema, and patchy or diffuse superficial scaling of the face and neck have been reported among women; while patchy erythema without scale is seen on the clean shaven faces of men. In these occupational reports, fair-skinned individuals are more frequently affected.
Histology The histology of dry skin is rarely considered in textbooks of dermatopathology. A group of investigators have reported that they consider asteatotic eczema to be similar histologically to seborrheic dermatitis, with focal scattered parakeratosis, minor acanthosis, and a scattered inflammatory infiltrate. In aged dry skin, the epidermis may be flat, atrophic, and accompanied by a compact SC. The number of cell layers is typically increased compared to younger individuals. 75In aggravated cases,asteatotic eczema may merge into the picture of nummular eczema
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Figure 2.
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Xerotic skin with a pattern resembling cracked china (eczemacraquele)
with spongiosis. The sebaceousglands may be small or absent in asteatotic areas.@ Hemorrhagic fissuring in eczema craquele has been described by an investigator as showing splitting of the SC, with upward curling of the free edge away from the crack.s7 Deeper fissuring resulted in damage to superficial blood vessels and hemorrhage.
Differential
l
Diagnosis
A number of dermatologic and systemic conditions may manifest as dry appearing skin. Atopic dermatitis and ichthyosis vulgaris are probably the most common. In atopic dermatitis, there is rough, dry appearing skin often involving the flexures. Lichenification may be present. Ichthyosis vulgaris usually begins in childhood, with dry appearing skin and prominent scaling that often spares the flexures4 Biopsy of ichthyosis vulgaris usually demonstrates an absent or markedly decreased granular cell layer. Dry appearing skin, sometimes under the heading of ichthyosis-like or eczema craquele, has been described in association with AIDS, Hodgkin disease, mycosis fungoides, hypothyroidism, sarcoidosis, myeloma, chronic zinc deficiency, and internal carcinoma and with certain drugs.-1,*,89-y0These include triparanol, nicotinic acid, butyrophenones, isotretinoin, etretinate, and, rarely, cimetidine. 213It is to be expected that drugs involved with lipid metabolism might affect barrier lipids.
Management The management of dry skin conditions is well known to most dermatologists and includes manipulation of bathing habits in conjunction with the use of emollients, occlusive formulations and humectants. It has been reviewed extensively. 9J,92The traditional view that petrolatum acts simply as an external barrier has recently been questioned. 93 Petrolatum applied topically after barrier disruption of the skin was actually found within the intercellular space of the stratum corneum at all levels. Likewise, glycerol has been shown to correct the abnormal degradation of desmosomes that is present in dry skin.65 In occupational settings where decreased air moisture precipitates “low humidity occupational dermatoses”, engineering changes that increase relative humidity may be curative. Home humidifiers may also be of benefit, but these must be cleaned properly to prevent aerosolization of bacteria.
Conclusions It is likely that dry skin conditions will continue to be a major problem in dermatological practice into the 21st century. Dermatologists who are familiar with the recognition and management of such problems, will make a major contribution to the comfort and well-being of these patients both at home and on the job.
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Acknowledgment Dr. Steven R. Cohen provided valuable assistancein the preparation of this review.
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ysis of ceramides within the stratum corneum in relation to seasonal changes. Dermatology 1994;188:207-214. Imokawa G, Abe A, Jin K. Decreased level of ceramides in stratum corneum of atopic dermatitis: An etiologic factor in atopic dry skin? J Invest Dermatol 1991;96:523-6. Denda M, Koyama J, Hori J, et al. Age- and sex-dependent change in stratum corneum sphingolipids. Arch Dermatol Res 1993;185:415-7. Rawlings A, Mayo A, Rogers J, et al. Aging and the seasons influence stratum corneum lipid levels (abstract). J Invest Dermatol 1993;101:483. Rawlings AV, Scott IR, Harding CR, et al. Stratum corneum moisturization at the molecular level. Prog Dermato 1994;28:1-12. Onken HD, Moyer CA. The water barrier in human epidermis. Arch Dermatol 1963;87:90-6. Grubauer G, Feingold KR, Harris RM. Lipid content and ipid type as determinants of the epidermal permeability barrier. J Lipid Res 1989;30:89-96. Abrams K, Harvell JD, Shriner D, et al. Effect of organic solvents on in vitro human skin water barrier function. J Invest Dermatol 1993;101:609-13. Imokawa G, Hattori M. A possible function of structural lipids in the water-holding properties of the stratum corneum. J Invest Dermatol 1985;84:282-4. Thompson GA. Lipid modification during epidermal cell differentiation. J Dermatol 1993;20:667-73. Potts RO. Stratum corneum hydration: Experimental techniques and interpretations of results. J Sot Cosmet Chem 1986;37:9-33. Querleux B, Richard S, Brittoun J, et al. In vivo hydration profile in skin layers by high-resolution magnetic resonance imaging. Skin Pharmacol 1994;7:210-6. Hashimoto-Kumasaka K, Horii I, Tagami H. In vitro comparison of water-holding capacity of the superficial and deeper layers of the stratum corneum. Arch Dermatol Res 1991;283:342-6. Hori M, Kligman AM. Light microscopic and transmission electron microscopic investigations of the stratum corneum of xerosis vulgaris of the leg. J Dermatol 1989; 16:296-302. Warner RR, Myers MC, Taylor DA. Electron probe analysis of human skin Determination of the water concentration profile. J Invest Dermatol 1988;90:218-24. Hansen JR, Yellin W. NMR and infrared spectroscopic studies of stratum corneum hydration. In: Jellinek HHG, editor. Water structure at the water polymer interface. New York-London: Plenum Press, 1972:19-28. Middleton JD. The mechanism of water binding in stratum corneum. Brit J Dermatol 1968;80:437-50. Ackerman AB. Xerosis, asteatosis, asteatotic eczema, eczema craquele; and dry skin? In: Ackerman AB. Ackerman’s resolving quandaries in dermatology, pathology and dermatopathology. Baltimore: Williams & Wilkins, 1995:323-4. Leveque JL, Grove G, de Rigal J, et al. Biophysical characterization of dry facial skin. J Sot Cosmet Chem 1987; 82:171-7. Rawlings A, Hope J, Rogers J, et al. Skin dryness-What is it? (abstract). J Invest Dermatol 1993;100:510. Rawlings A, Harding C, Watkinson A, et al. The effect of
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76.
77.
78. 79. 80. 81. 82. 83.
84.
85.
86.
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glycerol and humidity on desmosome degradation in stratum corneum. Arch Dermatol Res 1995;287:457-64. Horii I, Nakayama Y, Obata M, et al. Stratum corneum hydration and amino acid content in xerotic skin. Br J Dermatol 1989;121:587-92. Kligman AM. Perspectives and problems in cutaneous gerontology. J Invest Dermatol 1979;73:39-46. Jacobson TM, Yuksel KU, Geesin JC, et al. Effects of aging and xerosis on the amino acid composition of human skin. J Invest Dermatol 1990;95:296-300. Loden M. Biophysical properties of dry atopic and normal skin with special reference to effects of skin care products. Acta Derm Venereol Suppl (Stockh) 1995;192:1-48. Saint-Leger D, Francois AM, Leveque JL, et al. Stratum corneum lipids in skin xerosis. Dermatologica 1989;178: 151-5. Rogers J, Harding C, Mayo A, et al. Stratum corneum lipids: The effect of ageing and the seasons. Arch Dermato1 Res 1996;288:765-70. Akimoto K, Yoshikawa N, Higaki Y, et al. Quantitative analysis of stratum corneum lipids in xerosis and asteatotic eczema. J Dermatol 1993;20:1-6. Ghadially R, Brown BE, Sequeira-Martin SM, et al. The aged epidermal permeability barrier. Structural, functional, and lipid biochemical abnormalities in humans and a senescent murine model. J Clin Invest 1995;95:2281-90. Thune I’. The effects of detergents on hydration and skin surface lipids. Clin Dermatol 1996;14:29-33. Hara M, Kikuchi K, Watanabe M, et al. Senile xerosis: Functional, morphological, and biochemical studies. J Geriatr Dermatol 1993;1:111-20. Aisen E, Shah-an, Gilhar A. Sebum and water content in the skin of aged immobilized patients. Acta Derm Venereol (Stockh) 1997;77:142-3. Mitchell JC. Percentage humidity of the air in a dermatological ward-xerosis of the skin and irritant contact dermatitis. Contact Dermatitis Newsletter 1972;11:287-90. Rycroft RJG, Smith WDL. Low humidity occupational dermatoses. Contact Dermatitis 1980;6:488-92. White IR, Rycroft RJG. Low humidity occupational dermatosis-An epidemic. Contact Dermatitis 1982;8:287-90. Rycroft RJG. Low-humidity occupational dermatoses. Dermatol Clin 1984;2:553-9. Rayman RB. Passenger safety, health, and comfort: A review. Aviat Space Environ Med 1997;68:432-40. Thibeault C. Cabin air quality. Aviat Space Environ Med 1997;68:80-2. Sherertz EF, Storrs FJ. Contact dermatitis. In: Rosenstock L, Cullen MR, editors. Textbook of clinical occupational and environmental medicine. Philadelphia: WB Saunders, 1994:514-29. Halkier-Sorensen L, Menon GK, Elias PM, et al. Cutaneous barrier function after cold exposure in hairless mice: A model to demonstrate how cold interferes with barrier homeostasis among workers in the fish-processing industry. Br J Dermatol. 1995;132:391-401. Proksch E, Brasch J. Influence of epidermal permeability barrier disruptions and Langerhans’ cell density on allergic contact dermatitis. Acta Derm Venereol (Stockh) 1997; 771102-4. James WD, editor. Military dermatology. Textbook of mil-
Chits
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itary medicine. Part III. Disease and the environment. Washington DC: Office of the Surgeon General, 1994. 87. Caplan RM. Superficial hemorrhagic fissures of the skin. Arch Dermatol 1970;101:442-51. 88. Mehregan AH, Hashimoto K, Mehregan DA, et al. Pinkus’ guide to dermatohistopathology. 6th ed. Norwalk: Appleton & Lange, l995. 89. Kutting B, Metze D, Luger TA, et al. Mycosis fungoides presenting as an acquired ichthyosis. J Am Acad Dermato1 1996;34:887-9.
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90. Weismann K, Wadskov S, Mikkelsen HI, et al. Acquired zinc deficiency dermatosis in man. Arch Dermatol 1978; 114(1):1509-11. 91. Lazar AI’, Lazar P. Dry skin, water, and lubrication. Dermat01 Clin 1991;9:45-51. 92. Draelos ZD. Cosmetics in dermatology. 2nd ed. New York: Churchill Livingstone 1995:83-95. 93. Ghadially R, Halkier-Sorensen L, Elias PM. Effects of petrolatum on stratum corneum structure and function. J Am Acad Dermatol 1992;26:387-96.
The EfSect DONALD
RUDIKOFF,
of Dryness
on the Skin
MD
after she had bathed him and anointed him with oil forth from the bath he came, in bearing like the immortals Homer, Tlze Odyssey1 . water giveth and water taketh away .
Shelley and Shelley2 ractitioners of medicine have recognized the importance of water for human life since time imP memorial; yet, until quite recently, there has been scant mention in the literature about the effects of water loss on the skin, and it is likely that dryness of the skin is, for the most part, a modern phenomenon. A thorough review of the subject in 1972, led one clinical investigator to conclude, ‘I. . . man-made environment has become the most common cause of an increasing incidence of dry skin and of the variety of cutaneous conditions resulting from this. Cleansing agents . . . and rapid changes of temperature and humidity universally encountered either in overheating or air conditioning in homes, offices, airliners, and automobiles are among the modern, everyday environmental factors that contribute to the almost universal occurrence of dry skin of people living in the cities and the suburbs . . . .“g During the last 25 years great strides have been made in understanding the mechanisms by which the integument retains moisture and regulates the body’s “aquatic milieu”; however, dry skin remains one of the most common and vexing human disorders. Ubiquitous advertisements for moisturizers and the profusion of skin-care books attest to the magnitude of the problem. This paper will examine the historical, clinical, and pathophysiologic aspects of dry skin and related dermatoses, as well as the impact of dry atmospheric conditions on the skin.
Definition The term xerosis or “dry skin” is used interchangeably by physicians, patients, and the cosmetic industry to describe a dermatosis with features of roughness, flaking, scaling, fissuring and apparent lack of moisture.4,” The condition is frequently associated with an atopic state and varying degrees of ichthyosis vulgaris. There -.____
.__--
From the DepartmerIt of Dermatology, Mount Sinai Medical Center. New York, Nezu York. Address correspondence to Donald Rudikoff, M.D., Box 1048, The Momf Sinc7i Medical Center, One Gustave L. Levy Place, New York, N1 10029-6574.
0 1998 by EfsezTier Science Inc. 655 Az~enur of the Americas, Neul York,
NY 10020
is no uniformly reproducible definition for xerosis, and a number of terms based on symptomatology, physical signs, and presumed etiology are used synonymously by clinicians.6 These include xerosis, xeroderma, asteatosis, asteatotic dermatitis, winter itch, rough skin and chapping. This terminology, to a Iarge extent, reflects the misapprehension of early practitioners who speculated that dry skin was caused by an absolute or relative deficiency of sebaceous secretions.7,8Another term, reserved for severely inflamed and dry skin resembling cracked porcelain, eczema craquele, has aptly been described as “a rare form of eczema . . . in which a reddened surface is covered with large, thin flakes or scales, separated and outlined in polygonal areas by superficial cracks or fissures.“8 The dry appearance of skin is now generally accepted to be a consequence of the scattering and reflection of light off a rough surface that results from abnormal desquamation. In reality, not all skin that appears or feels dry is actually dry.“rY Consider the dry itchy skin of both chronic renal failure and old age, which typically have a normal moisture content.iOJ1 For accuracy, an investigator recommends specifying the following qualities when describing xerosis: (1) rough versus smooth; (2) seborrheic versus asteatotic; and (3) dry versus hydrated.6
History Early authors recognized the occurrence of dry pruritic skin under winter conditions. While exploring the history of “Dermatitis Hiemalis,” a group of investigators traced the expression “winter itch” to a seminal publication by LA Duhring published in 1874.12,‘”Duhring ascribed a “neurosis” of the skin to symptoms of pruritus, smarting, tingling, and burning that appeared in the fall, about the time of the first frost. The symptoms were of sudden onset, increased in the evening, and were exacerbated by heated rooms and hot stoves. Physical findings were minimal at first, with only dry appearing skin. Subsequently, the skin might become “rough and harsh”, displaying “redness, inflammation, and irritated hair follicles, with many hairs broken off short” . . . The usual sites of involvement were the extremities, especially the calves. Another investigator termed the condition “winter prurigo,” and at least one author mistakenly attributed it to constipation.i4J5 Variations in temperature were thought by some authors to be as important as frosty air alone.lh In 1891, an investigator described a dermatitis with a 0738-081X/98/$19.00 PI1 SO738-081Xf97)00173-9
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predilection for the dorsa of the hands and feet that related to low temperature, low humidity, and wind during the cold winters of Cleveland, Ohio.17 Travel to a warmer climate provided relief. In 1912, this investigator and his colleague answered criticisms that the etiological factor might be a dermatophyte by citing the lack of such organisms on pathological examination and observing that the condition occurred more frequently in the winter months when tinea was less common.18 Subsequent reports further validated the concept of a xerotic skin disorder with a seasonal predilection.19JO Travel from the tropics to a cooler, dryer climate was also implicated as a cause of dry skin in soldiers and civilians’i Decades later, while seeking a more quantitative explanation for the phenomenon of “winter itch,” a group of investigators related chapping of the skin to dry air as measured by dew point (ie, the temperature at which the moisture in the air begins to condense into visible form).22 They emphasized that symptoms of chapping were often preceded by moist air conditions, followed by a sudden drop in air moisture; and they noted that cooler ambient air, with a low moisture content, tended to be dried even further by indoor heating. In 1962, an investigator reported a pruritic skin condition identical to dermatitis hiemalis occurring during the summer months in Texas.23The condition resulted from long periods of exposure to air conditioning alternating with short exposures to a hot, humid environment. Paralleling the clinical recognition of dry skin conditions and their relationship to weather, travel, and environmental manipulations, the late 20th century has been marked by advances in our understanding of epidermal structure, skin hydration, permeability, and barrier function.
Physiology of Skin Barrier Function
Hydration
and
The skin is a complex structure that affords protection from the external environment. The major barrier to water loss from the body resides in the outermost portion of the skin, the stratum corneum (SC). It has been suggested that the main purpose of the epidermis is to generate this tough protective layer.z4 The SC is heterogeneous in structure, and it has been likened to a brick wall in which the noncontinuous, mostly proteinaceous, component, the corneocytes (bricks), are embedded in a continuous matrix of intercellular lipid (mortar).2s The SC consists of about 15 layers of flat corneocytes that are devoid of intercellular organelles and cytoplasm. They consist mostly of a core of bundled keratin filaments surrounded by a rigid cornified envelope.26 Filaggrin, a histidine-rich protein formed from the
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short-lived precursor protein profilaggrin, is the other major protein of the horny cells. Although it aggregates keratin fibers in vitro, this may not be the case in vivo.27 It is hydrolyzed further to amino acids and other compounds that are collectively known as natural moisturizing factors (NMF), with plasticizing, moisture-retaining and ultraviolet protective characteristics.2*,*9 The individual corneocytes have overlapping edges, and they are bound by corneodesmosomes whose disintegration is linked with desquamation.*5JO They may vary in size, depending on age, anatomic location, and upon conditions that influence epidermal proliferation, such as UV radiation.2” When there is an increase in the epidermal turnover rate, there may be a disruption of the orderly stacking. The result is a loss of barrier function.30 The SC thus serves as a barrier to evaporative water loss, and it also contains moisture within its substance.
Barrier
Function
of the Stratum
Corneum
Water reaches the skin surface via the eccrine sweat and by diffusion through the epidermis, limited only by the low permeability of the SC.31 The approximate transepidermal water loss (TEWL) of an average adult ranges from 85 to 170 ml per day. At rest, with no visible perspiration, the loss from eccrine sweat glands is about 300 to 500 ml per day, much of which is from the palms and soles.a’ Under very hot conditions, as much as 2 liters per hour may be lost as sweat.32 The TEWL from diffusion through the epidermis varies from 0.2-0.6 mg/cm*,/h, and it may vary in different parts of the body.“a-35 It is well-known that hydration dramatically increases the permeability of the skin;31 in addition, increases in skin temperature can increase the TEWL independent of sweating.“6 Water diffusion through the SC is by passive diffusion, a function of water-vapor gradient determined by ambient conditions.31 There is no evidence of active transport of water through the horny layer, and the contribution of the cutaneous appendages to the TEWL is minimal, owing to their small total cross-sectional area relative to the entire skin surface.37 Prior to the 20th century, the skin was considered impermeable, except possibly to gases.37By the beginning of this century, the skin was accepted to be relatively impermeable to water and electrolytes and somewhat permeable to lipid-soluble substances. The barrier to diffusion in the skin, once considered to be in the stratum lucidum, is now thought to be located in the SC throughout most of its thickness, and not just a small layer at its base.37-39 The suppleness of the skin once attributed to its fat content, was established by an investigator to be a function of the moisture it contains”0 This researcher
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postulated the existence of water soluble, “mucoid or mucoprotein” substances responsible for the water binding properties of the horny layer. Later termed “natural moisturizing factors” (NMF), these could be extracted with water from the SC only after solvent extraction of the lipids.41,42 The intercellular layer of the SC ranges in thickness from 0.3 nm to 20.6 nm, and it is filled with a nonhomogeneous material and lipid derived from the lamellar bodies formed in the spinous and granular layers.?5J” They expel their contents, including lipid, polysaccharides, and hydrolytic enzymes into the intercellular space, increasing the net intercellular volume and decreasing the volume within the cells. During the process of epidermal differentiation, there is a significant change in the composition of epidermal lipids, with an increase in fatty acids and ceramides and marked decrease in phospholipids.4” Simple glycosphingolipids, cholesterol sulfate, free sterols, and sterol esters are also found. The lipid composition of the skin may vary with age, sex, body site, and season.45-4”It is noteworthy that in some patients, during the winter months, there is a decreased proportion of ceramides, cholesterol, and fatty acids, with its implication for winter xerosis; though in young adults, ceramide mass remains relatively stable at various skin locations, even with change of season.45,48,49 There is good evidence, mostly from studies of epidermal permeability after solvent extraction of SC lipids, that these molecules are crucial for the barrier function in the skin and are probably more important than the actual thickness of the SC.44,50-52 Structural lipids, especially ceramide in the intercellular spaces, play a critical role in the water-holding properties of the SC.-5?Unlike the typical bilayer configuration seen in membranes, the lipid portion of the intercellular lamellae often consists of several alternating bilayers and monolayers?
Hydration Moisturizing
of the SC and Natural Factors
The state of hydration of the SC is governed by three factors: (1) water that reaches it from below, either from sweating or transepidermal transport; (2) water lost from the surface by evaporation; and (3) the ability of the horny layer to hold moisture.31 In addition, because of its contiguity with the underlying epidermis, the water content in the lower horny layer must be higher than at the surface, and, in fact, a gradient exists within the SC.37It is well-known that the ever changing ambient relative humidity can influence the hydration and water flux across the SC in a complex manner as determined by Fick’s law.55 Thus, the degree of hydration is never constant; and as long as the relative humidity is less than IOO%, there will be a net outward diffusion of
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water from the lower layers of the epidermis.x7 A group of investigators using magnetic resonance imaging (MRI) delineated two distinct areas within the SC of heel skin: an outer layer, where water content could be modified by external mechanisms, and an inner layer not altered by such manipulations.56 The midlayer of the SC has the highest content of extractable amino acids and the greatest water holding capacity.57,58 A number of different methods to assessthe water content of skin have been developed. These include analysis of water flux, electrical measurements (resistance, capacitance and impedance), heat conductivity, photoacoustic spectroscopy, viscoelastic properties, microwave propagation, dye fluorescence, topography, infrared spectroscopy, near-infrared reflectance spectroscopy, electron-probe analysis, and nuclear magnetic resonance imaging.55,56,59 The three species of water identified in the SC are: (1) tightly bound primary water of hydration bonded to polar sites on SC proteins; (2) secondary water, probably hydrogen-bonded, less tightly, to primary water of hydration, which increases in amount up to about 40% total water content, and (3) bulk liquid water, which does not appear until about 40 percent total water content is reached.6” It is the secondary water that is most dependent on the presence of natural moisturizing factors (NMF) and is most sensitive to changes in ambient humidity. The skin contains hydrophilic nitrogenous compounds that enable it, in part, to hold moisture.42 Extraction of these compounds results in a markedly diminished capacity for water retention. These natural moisturizing factors that make up as much as 10% of the dry weight of SC cells consist of a mixture of amino acids or their derivatives, including urea, urocanic acid, and, most importantly, 2-pyrrolidone-5-carboxylic acid.4y The latter constitutes about 2% of the dry weight of the SC, yet is virtually absent from other tissues and organs of the body .29,42,61 The natural moisturizing factors are derived from the breakdown of filaggrin as cells reach the SC. This breakdown is timed precisely and elegantly to the stage just after the permeability barrier is being formed.ay
Physiology
of Dry Skin
Much work has been done to delineate the physiological characteristics of xerotic skin. What we call dry skin may just be scaly skin. 62In a study of facial dry skin, conductance, a measure of hydration, and extensibility decreased with increasing skin dryness.e? This suggested that winter dry skin may result either in a drier or thicker SC. Severity of dry skin was associated with a decreased size of exfoliated keratinocytes. Patients with senile pruritus have also been shown to have increased intracorneal cohesion and altered skin surface
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RUDIKOFF
contour parameters, suggesting an acquired abnormality of keratinization. The SC may become thicker and more hyperkeratotic if desquamation is abnormal. The SC cells may be shed together in large scalesrather than individually.25 In healthy skin, as keratinization progresses, desmosomes tend to be degraded. Thus allowing detachment and shedding of corneocytes. This is reflected in decreased levels of desmoglein-I in the outer stratum corneum. In a study of dry skin, the normal degradation of desmosomes did not occur, and desmoglein I levels remained high;@ moreover, desmosomal degradation is humidity-dependent, and it is reduced if the relative humidity is low.65 A good deal of work has been done on the actual water content of dry appearing skin using a variety of methods. A decrease in hydration and of extractable amino acid content of the SC has been demonstrated in dry skin of elderly patients, even though water content of whole skin including dermis is normal in these patients.66,h7Xerosis does not seem to alter the amino acid content in younger subjects.68 Certainly it is far from clear that water content is decreased in all so-called dry skin conditions, although this does seem to be the case in the dry appearing skin of atopic dermatitis and psoriasishy Because SC lipids are so important for epidermal barrier function, it would seem reasonable to expect that there might be an alteration of these lipids in xerosis. There does seem to be a decrease in SC lipids with age, but not with xerosis and asteatotic eczema.70-72Transepidermal water loss does not seem to be increased with age as might be expected, and it actually decreases;73however, aged skin may be more sensitive to environmental insults and recover more slowly than the skin of younger individuals.67 The relative importance of sebum-derived lipids toward the etiology of dry skin is controversial. They probably do not affect the moisture content of the skin to any great extent, but they may influence skin surface texture.74 A group of investigators consider decreased hydration of the skin surface in aged skin to be the result of a decrease in surface lipids due to reduced sebum secretion as well as a decrease in NMF due to poorly developed keratohyaline granules.75 Another group found decreased sebum production in older patients, but skin hydration was normal except in those who were immobilized.7h
Clinical
Presentation
The dermatologist is likely to encounter xerosis in a number of clinical settings. During the winter, especially in locales with low humidity, the relative humidity will drop indoors as a result of heating already dry air. Earlier in this century, with the advent of steam
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heat, a pot of water on the radiator became the poor person’s humidifier. Dry environmental conditions may be encountered in the home, on the job, on public and private conveyances, and in other situations. The patient may be older, with scrupulous hygiene, and may over-bathe. Elderly patients frequently continue the bathing habits of youth, with resultant dehydration of the skin. Dry skin conditions have been described in hospital wards, and in work environments where the humidity is kept low.77 A group of investigators described an occupational dermatosis occurring in workers at a telephone exchange installation, where the relative humidity was maintained at about 35% to protect metal contacts on electrical equipment.78 Similar circumstances have been described in factories that manufacture silicon chips and soft contact lenses, and they may occur in offices, in airplanes among flight crews, and high-altitude pilots.78-80 The dryness of the air in commercial aircraft is wellknown, with relative humidities in the range of 1217%.81,82The reason for this is that air at high altitudes has a low water content, and aircraft engineering constraints limit on-board humidification systems. Dry skin conditions may also be seen among hotel workers and traveling salesmen, as well as truck drivers exposed to dry air from heaters; and dry skin has been reported as a significant problem in the military.83 Dry skin and eczema are often encountered in the fishprocessing industry. 84Chapping of the skin and water loss from working in a hot or cold, dry environment can predispose the skin to penetration by some chemical irritants, resulting in irritant contact dermatitis.83 An investigator reported that xerosis seems to be a form of irritant contact dermatitis, the irritants being adverse atmospheric conditions, friction, and exposure to soap and water.3 Dry, irritated skin may be more susceptible to allergic contact allergens; and there is evidence that perturbations of the skin-barrier function may induce a greater concentration of Langerhans cells.85 Initially, dry skin may present merely as pruritus that is paroxysmal, exacerbated by woolen clothing and worse at night, when the patient is not as involved with the activities of daily life. 13In the elderly there may be disabling, unrelenting itch with minimal physical signs.9 Facial pruritus has been reported in the setting of low humidity in the workplace, especially if local heat sources are present.78 Conditions of increased air movement, such as high winds and exposure to unhumidified air from vents may exacerbate dry skin. 9 As previously noted, although such conditions are more prevalent during the winter, similar changes have been described in hot climates with air conditioning.2” This effect is enhanced by prior wetting of normal skin, particularly in individuals prone to xerosis. In addition, hot, dry and windy
Clinics in Dermatology
Figure 1.
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1998;16:99-107
Xerotic skin with grayish-white,
THE EFFECT OF DRYNESS ON THE SKIN
cobweb-like accentuation
conditions encountered in desert climates can cause dryness and failure of sweat glands.86 The clinical manifestations of dry skin range from a rough, dry appearance to erythema, scaling, and excoriation. The earliest changes typically consist of a subtle, dull grayish-white, cobweb-like accentuation of normal skin furrows (Fig 1).23Individuals with darker skin may complain of a surface ashiness; moreover, the skin surface is likely to appear rough and uneven. With progressive dryness, tiny cracks (chaps or fissures) may develop in a retiform pattern resembling cracked china, with slight elevation of the free edges of the scales (Fig 2). With abnormal desquamation and irritation, fullblown eczema craquele may develop, much like cracks in dry mud.4 These polygonal “shrinkage cracks,” also seen in rock, concrete, and paint, are well-known to geologists and engineers. 87 An investigator has described painful hemorrhagic fissures of the skin on the legs of elderly patients with xerosis, eczema craquele, and underlying edema.87 If there is a pre-existing dermatosis, such as ichthyosis vulgaris or atopic dermatitis, there may be an exacerbation of the underlying condition. Many patients will have scaly skin on the anterior and lateral surface of the legs, with linear scratch marks, dried up blood, and hairs broken off close to the follicular orifices.13Similar changes may also occur to a lesser degree on the upper extremities, as may chapping and fine scaling of the inner thighs and flanks. Redness and
of normal skin furrows
103
as well as pair@1 fissuring.
chapping is common on the dorsa of the hands, especially in the setting of frequent hand washing, as encountered among health-care professionals and restaurant workers. Painful fissuring, sometimes hemorrhagic in nature, may develop on the fingertips near the lateral nail margins (Fig 1). Workers with “low humidity dermatoses” have been noted to have pruritus and urticarial whealing as a result of scratching. This occurs mostly on the covered parts of the body. 78 Erythema, edema, and patchy or diffuse superficial scaling of the face and neck have been reported among women; while patchy erythema without scale is seen on the clean shaven faces of men. In these occupational reports, fair-skinned individuals are more frequently affected.
Histology The histology of dry skin is rarely considered in textbooks of dermatopathology. A group of investigators have reported that they consider asteatotic eczema to be similar histologically to seborrheic dermatitis, with focal scattered parakeratosis, minor acanthosis, and a scattered inflammatory infiltrate. In aged dry skin, the epidermis may be flat, atrophic, and accompanied by a compact SC. The number of cell layers is typically increased compared to younger individuals. 75In aggravated cases,asteatotic eczema may merge into the picture of nummular eczema
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Clinics in Dermatology
Figure 2.
1998;16:99-107
Xerotic skin with a pattern resembling cracked china (eczemacraquele)
with spongiosis. The sebaceousglands may be small or absent in asteatotic areas.@ Hemorrhagic fissuring in eczema craquele has been described by an investigator as showing splitting of the SC, with upward curling of the free edge away from the crack.s7 Deeper fissuring resulted in damage to superficial blood vessels and hemorrhage.
Differential
l
Diagnosis
A number of dermatologic and systemic conditions may manifest as dry appearing skin. Atopic dermatitis and ichthyosis vulgaris are probably the most common. In atopic dermatitis, there is rough, dry appearing skin often involving the flexures. Lichenification may be present. Ichthyosis vulgaris usually begins in childhood, with dry appearing skin and prominent scaling that often spares the flexures4 Biopsy of ichthyosis vulgaris usually demonstrates an absent or markedly decreased granular cell layer. Dry appearing skin, sometimes under the heading of ichthyosis-like or eczema craquele, has been described in association with AIDS, Hodgkin disease, mycosis fungoides, hypothyroidism, sarcoidosis, myeloma, chronic zinc deficiency, and internal carcinoma and with certain drugs.-1,*,89-y0These include triparanol, nicotinic acid, butyrophenones, isotretinoin, etretinate, and, rarely, cimetidine. 213It is to be expected that drugs involved with lipid metabolism might affect barrier lipids.
Management The management of dry skin conditions is well known to most dermatologists and includes manipulation of bathing habits in conjunction with the use of emollients, occlusive formulations and humectants. It has been reviewed extensively. 9J,92The traditional view that petrolatum acts simply as an external barrier has recently been questioned. 93 Petrolatum applied topically after barrier disruption of the skin was actually found within the intercellular space of the stratum corneum at all levels. Likewise, glycerol has been shown to correct the abnormal degradation of desmosomes that is present in dry skin.65 In occupational settings where decreased air moisture precipitates “low humidity occupational dermatoses”, engineering changes that increase relative humidity may be curative. Home humidifiers may also be of benefit, but these must be cleaned properly to prevent aerosolization of bacteria.
Conclusions It is likely that dry skin conditions will continue to be a major problem in dermatological practice into the 21st century. Dermatologists who are familiar with the recognition and management of such problems, will make a major contribution to the comfort and well-being of these patients both at home and on the job.
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Acknowledgment Dr. Steven R. Cohen provided valuable assistancein the preparation of this review.
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