- Email: [email protected]
photodamage and photoprotection
Volume 24 Number 2, Part 1 February 1991
surgery. There are many factors that contribute to tbis, but probably the key one is the recruitment of Mohs mi crographic surgeons into academic positions. This has given dermatologic surgery significant acceptance among surgical specialties, enhanced patient care, and has im proved surgical training in dermatology residency. It was this surgical training, documented in the annual resident reports of the American Board of Dermatology, that was the basis for the acceptance of the new special require ments for dermatology by the Accreditation Council for Graduate Medical Education. Each residency review committee is obligated to review its special requirements on a regular basis and make changes in them to reflect the educational practice in res idency training. Therefore modifications in special re quirements actually reflect changes that have already oc curred in residency programs. From the data of the an nual resident reports to the American Board of Dermatology it was determined that more than 90% of the residents were being trained in flap and graft surgery and almost an equal number in laser treatment. Therefore the new special requirements, based on current educa tional practice, state: "The surgical training should be di rected by faculty who have had advanced training in der matologic surgery. Dermatologic surgical training should include electrosurgery, cryosurgery, laser surgery, nail surgery, biopsy techniques, and excisional surgery with appropriate closures, including small flaps and grafts when indicated." These requirements went into effect Jan. 1 of this year. These special requirements are additions to, and not a substitution for, the established and required training in the basic, laboratory, and clinical sciences that the Res idency Review Committee and the American Board of Dermatology are committed to maintain. However, the new special requirements confer to dermatology official recognition by organized medicine of the specific listed procedures and acknowledge dermatology as a medical and surgical specialty. Dermatologic surgical fellowships, such as Mohs mi crographic surgery, are one of the formalized ways to ob tain more extensive surgical training than may be ob tained in residency, but it is not the only way. Preceptor ships and other postgraduate education and instruction are some of the other avenues available for attaining ad ditional surgical skills. These methods are used by other specialists such as otolaryngologists, ophthalmologists, and plastic surgeons to gain practical knowledge and ex perience in new techniques that were not taught at the time of their residencies. For example, this is the means by which many dermatologists have learned laser surgery and surgeons laparoscopic cholecystectomy. It is also the way in which all specialists who' completed residencies before 1982 have learned liposuction. These educational channels for the postgraduate acquisition ofnew skills and competence are commonly used and are an important
Correspondence 315 process to allow physicians to grow in knowledge and abilities beyond those that were available or taught in residency. It is clear, however, that these new capabilities are more readily and proficiently acquired if the founda tion for them is part of residency training. This founda tion for dermatologic surgery is being achieved currently in dermatology residencies and is reinforced and sup ported by the new special requirements for dermatology. In summary, there is strong support and agreement for Dr. Jones' position on the need to maintain excellence in the basic, laboratory, and clinical sciences in dermatology residency. The new special requirements for dermatology are additional provisions, not substitutions, thatreflect the current educational practice in the vast majority of resi dency training programs. Thus they are the results of ev olutionary changes in our specialty, not the whims of a surgical minority. These acknowledge by organized med icine that dermatology is a medical and surgical specialty. These developments present special challenges and offer notable opportunities for our specialty. E. A. Krull, MD Department of Dermatology Henry Ford Hospital 2799 W. Grand Blvd. Detroit, MI48202-2689 REFERENCE
1. Tromovitch TA, Stegman SJ. Microscopically controlled excision of skin tumors. Arch Dermatol 1974;110:231.
Photoagingjphotodamage and photoprotection To the Editor: We read with interest the CME article by Taylor, Stern, Leyden, and Gilchrest (J AM ACAD DER· MATOL 1990;22;1-15). Because it is important to provide the most accurate and current information in continuing education articles, we haveseveral specific comments that differ with some ofthe information reported, and we be lieve they will be of interest to the dermatologic commu nity. Ample data now exist to show that para-aminobenzoic acid (PABA) does not bind to proteins to give "protection even after bathing, swimming, or perspiring" as the arti cle reports. PABA crystallizes on the skin's surface and is vulnerable to removal by water after as little as 10 min utes of water exposure.1-6 The proposed Food and Drug Administration (FDA) standard test for waterproofprod ucts is 80 minutes of water exposure. If a product is wa terproof by this standard, it may also claim to be sweat resistant. The Bonin and Gallagher work7• 8 that purported to demonstrate mutagenic and tumor-promoting properties of 2-ethylhexyl p-methoxycinnamate has been refuted. Extensive safety testing has demonstrated that the earlier
316
Journal of the American Academy of Dermatology
Correspondence
work was in error and that this sunscreen is not mutagenic or carcinogenic. 9. 12 Readers should be aware ofthese im portant studies because more and more commercial products contain the ingredient in question. Although the article by Taylor et al. maintains that a 2D-minute to 2-hour delay after sunscreen application and before sun exposure "is probably optimal," we are not aware of data to support a 2-hour delay other than in old publications on PABA in alcohol. 13 ,14 Currently mar keted sunscreen products are effective when initially ap plied. Although it is important to let a waterproof prod uct dry before water immersion to minimize wash-off, many consumers apply their sunscreen on the beach. We know of no data to support the idea that the efficacy of currently available products increases with time after ap plication. The statement that there are no standards for defining light source, skin type, and quantity of sunscreen for test ing the efficacy of sunscreens is surprising; all these topics are addressed in the 1978 FDA over-the-counter monograph. IS The sun protection factor (SPF) values that appear on the labels of U.S. products are generally valid if the user follows the detailed procedure set forth by the FDA in this document. We realize that the issue of international standards has not yet been resolved, but progress continues in this area. The 1982 Pathak article on outdoor testing J6 cited by Taylor et al. was updated in 1986 to include test results on many sunscreens in the ultra protection category (SPF 15 and higher), and it was found that their SPFs remained similar in indoor and outdoor tests. 17 Recent studies of commercial waterproof products with high SPFs have shown that their SPFs are similar indoors and outdoors and that they maintain their efficacy after swimming (M. Pathak and R. Sayre, manuscript in preparation). The life-table analysis method J8 for assigning the pro tection value of sunscreens has been criticized as imprac tical and imprecise. It requires up to 20 individual UV exposures over several days. If minimal erythema is not found atone ofthe given exposures, the minimal erythema dose (MED) is estimated. For products with no deter mined MED, an MED value is "assigned." This test pro cedure has not met with acceptance because it does not result in a defined, reproducible value. One article is cited to support the assertion that the amount of sunscreen usually applied is "probably less than half that recommended." Several other references indicate that, although the amount that is used varies, it is probably at or greater than 2 mg/cm2.19-23 At any rate, the amount used for SPF determination (2 mg/cm2) is just enough to cover the test site evenly and completely. Use of less would make the test result unreliable because of uneven spreading and would make product compari sons meaningless. 19, 23 The issue of application density has proved to be par ticularly troublesome for international standardization.
We are glad to report that the Commission Internation ale de L'Eclairage (CIE) has recently adopted 2 mg/cm2 as the appropriate application density in its guidelines. 24 Because we realize the importance of presenting the most up-to-date information, we hope you will print this letter soon as an update to your previous article.
Patricia Agin, PhD Schering-Plough Health Care Products 3030 Jackson Ave. Memphis, TN 38151 REFERENCES 1. Morasso MI, Thielemann AM, Pinto C, et ai. In vitro and in vivo study of the substantivity of p-aminobenzoic acid and two of its esters. J Soc Cosmet Chern 1985;36:355-62. 2. LeVee GJ, Sayre RM, Marlowe E. P-aminobenzoic acid as a sunscreen and its behavior on skin. Int J Cosmet Sci 1981;3:49-55. 3. Sayre RM, Marlowe E, Agin PP, et ai. Performance of six sunscreens on human skin. Arch Dermatol 1979;115:46-9. 4. Kaidbey KH, Kligman AM. An appraisal of the efficacy and substantivity ofthe new high-potency sunscreens. J AM ACAD DERMATOL 1981;4:566-70. 5. Pathak MA, Fitzpatrick TB, Greiter FJ, et aI. Principles of photoprotection in sunburn and tanning, and topical and systemic photoprotection in health and disease. J Dermatol Surg Oneal 1985;11:575-9. 6. Blank IB, Cohen JH, Anderson RR, et ai. Observations on the mechanism of the protective action of sunscreens. J In vest Dermatol 1982;78:381-5. 7. Bonin AM, Arlauskas AP, Angus DS, et al. UV-absorbing and other sun-protecting substances: genotoxicity of2-eth ylhexyl p-methoxycinnamate. Mutat Res 1982;105:303-8. 8. Gallagher CH, Greenoak GE, Reeve VE, et aI. Ultraviolet carcinogenesis in the hairless mouse skin: influence of the sunscreen 2-ethylhexyl methoxycinnamate. Aust J Exp BioI Med Sci 1984;62:577-88. 9. Baker RSU, Gallagher CH, Lane Brown MM. Sunscreen not mutagenic. Med J Aust 1980;2:284. 10. National Toxicology Program, U.S. Dept. of Health and Human Services, Technical Bulletin No.9, 1983. 11. Roche Research Reports Nos. 93336, 104840, 105032, 104902, 105005, 105024, 104916, Hoffman LaRoche! Givaudan Corp. 12. Forbes D, Davies RE, Sambuco CP, et al. Inhibition of so lar UVR-induced skin tumors in hairless mice by topical application of sunscreens. Report to The Givaudan Corpo ration, 1987. 13. Algra RJ, Knox JM. Topical photoprotectivc agents. Int J Dermatol 1978;17:628-34. 14. Pathak MA, Fitzpatrick TB, Frenk E. Evaluation of topi cal agents that prevent sunburn: the superiority of PABA and its esters in ethyl alcohoI. NEnglJ Med 1969;280:1459 63. 15. Department of Health, Education, and Welfare, Food and Drug Administration. Sunscreen drug products for over the counter human use. Fed Reg Aug. 25,1978;43:38206-9. 16. Pathak MA. Sunscreens: topical and systemic approaches for protection of human skin against harmful effects of so lar radiation. JAM ACAD DERMATOL 1982;7:285-312. 17. Pathak MA. Topical and systemic approaches for the pre vention of acute and chronic sun-induced reactions. Derm Clin 1986;4:321-34.
Volume 24 Number 2, Part 1 February 1991 18. Azizi E, Modan M, Kushelevsky AP, et al. A more reliable index of sunscreen protection based on life-table analysis of individual sun protection factors. Br J Dermatol 1987; 116:693-702. 19. Sayre RM. Sunscreen application: flawed study. Arch DermatoI1986;122:745. 20. Wiskemann A. Zur reproduzierbarkeit des lichtschutzfac tors. Fette Seifen Anstrichmittel 1968;70:361-4. 21. Hoppe U. Photostabilitat und hautaffinitat. J Soc Cosmet Chern. 1974;25:667-80. 22. Hoppe U. Factors determining the effectiveness of sun screening agents. Cosmet Sci 1980;2:147-9. 23. Schlagel CA, Sanborn EM. Weights of topical prepara tions required for total and partial body inunction. J Invest DermatoI1964;42:253-6. 24. CIE Photobiology and photochemistry technical committee division 6 TC12 final report: phototesting ofskin application for sun protection. September 1989.
Reply To the Editor: We thank Dr. Agin for her comments from the perspective of one directly involved in sunscreen development and evaluation. We wish to add only a few more comments from the perspective of physicians at tempting to interpret this now formidable literature for the benefit of their patients and colleagues. We are unaware of the ample data cited in Dr. Agin's unreferenced statement that para-aminobenzoic acid (PABA) does not undergo hydrogen binding to stratum corneum proteins and that PABA cannot provide some protection after bathing, swimming, or perspiring, as we stated in our article. We certainly did not mean to imply that PABA has high substantivity. Many other sunscreen ingredients are far superior in this regard, and sun· screens containing them are correctly advertised as "waterproof," whereas sunscreens containing PABA alone are not. With regard to the possible mutagenicity of 2-ethyl hexyl p-methoxycinnamate, of the four articles cited by Dr. Agin as refuting the works of Bonin, Gallagher, and their co-workers, the first article (for which Dr. Gallagher is a co-author) preceded the two positive studies, and the remaining three articles are unfortunately unavailable for all practical purposes to the medical community. We would encourage Dr. Agin and others with access to these data to publish a thorough and critical review of the mu tagenicity of all suspect sunscreen ingredients in a more accessible journal. With regard to the "optimal" period between applica tion of a sunscreen and exposure to the sun, it must be noted that ifthe user delays application until comfortably settled on the beach, he or she will probably receive more UV irradiation in transit, before the sunscreen is applied, than in the remainder of the day after an effective sunscreen has been applied. For this reason alone, we urge sunscreen manufacturers and physicians to recommend application of sunscreen well in advance of the intended sun exposure.
Correspondem:e 317 Although standards for light source, skin type, and quantity. of sunscreen were proposed . in a 1978 FDA monograph, they have also been addressed subsequently by several FDA"organized panels and argued by inter ested parties in a variety of formal and informal settingS. This continuing discussion suggests to us that neither the FDA nor the medical arid scientific communities are united in their recommendations. Surely the existence of FDA guidelines does not imply unanimity of opinion re garding the ideal sunscreen testing procedure. Weapologizefor having failed toreference Dr. Pathak's 1986 review. Our article does, however, note that indoor and outdoor SPFs tend to be similar for substantive sun screens, precisely Dr. Agin's point. With regard to the life-table analysis method for assigning a protection value to sunscreens, we agree that it has inherent difficulties. Our point is only that all methods have their difficulties. The amount of sunscreen applied by the average user is probably best considered to be unknown. However, of the four papers cited by Dr. Agin to indicate that it is greater than the 2 mgjcm2 used in SPF testing, one is a letter by Dr. Agin's co-worker criticiziIig the study we cited but providing no refuting data, and the other three are again essentially unavailable, although the titles sug gest that the amount of sunscreen spontaneously applied by casual users was not studied. Dr. Agin's related point, that SPF testing with less than 2 mgjcm2 of sunscreen would yield unreliable results, is irrelevant to the concern that many consumers apparently use sunscreens in this way and thus achieve far less protection than they assume. The elegant and effective sunscreens now available are testimony to the dedication and biochemical sophisti~a tion of the sunscreen industry, and they greatly facilitate the dermatologist's task of encouraging enlightened pre ventive health practices by the public. We concur com pletely with Dr. Agin that up-ta-date information regard ing these sunscreens should be readily available to dermatologists and to the public.
Barbara A. Gilchrest, MD,a Robert S. Stern, MD,b and Charles R. Taylor; MU Human Nutrition Research Center on Aging at Tufts University and Department ofDermatology, Boston University Medical School,a and Department of Dermatology, Beth Israel Hospital, Harvard Medical School,b Boston, Massachusetts
Athlete's nodules To the Editor: "Surfer's nodules" were one of the sports medicine-related injuries discussed in Dr. Basler's excel lent review of injury-induced cutaneous conditions assa ciatedwith athletic participation (J AM ACAO DERMA TOL 1989;21:1257-62). We recently described a 54-year
surgery. There are many factors that contribute to tbis, but probably the key one is the recruitment of Mohs mi crographic surgeons into academic positions. This has given dermatologic surgery significant acceptance among surgical specialties, enhanced patient care, and has im proved surgical training in dermatology residency. It was this surgical training, documented in the annual resident reports of the American Board of Dermatology, that was the basis for the acceptance of the new special require ments for dermatology by the Accreditation Council for Graduate Medical Education. Each residency review committee is obligated to review its special requirements on a regular basis and make changes in them to reflect the educational practice in res idency training. Therefore modifications in special re quirements actually reflect changes that have already oc curred in residency programs. From the data of the an nual resident reports to the American Board of Dermatology it was determined that more than 90% of the residents were being trained in flap and graft surgery and almost an equal number in laser treatment. Therefore the new special requirements, based on current educa tional practice, state: "The surgical training should be di rected by faculty who have had advanced training in der matologic surgery. Dermatologic surgical training should include electrosurgery, cryosurgery, laser surgery, nail surgery, biopsy techniques, and excisional surgery with appropriate closures, including small flaps and grafts when indicated." These requirements went into effect Jan. 1 of this year. These special requirements are additions to, and not a substitution for, the established and required training in the basic, laboratory, and clinical sciences that the Res idency Review Committee and the American Board of Dermatology are committed to maintain. However, the new special requirements confer to dermatology official recognition by organized medicine of the specific listed procedures and acknowledge dermatology as a medical and surgical specialty. Dermatologic surgical fellowships, such as Mohs mi crographic surgery, are one of the formalized ways to ob tain more extensive surgical training than may be ob tained in residency, but it is not the only way. Preceptor ships and other postgraduate education and instruction are some of the other avenues available for attaining ad ditional surgical skills. These methods are used by other specialists such as otolaryngologists, ophthalmologists, and plastic surgeons to gain practical knowledge and ex perience in new techniques that were not taught at the time of their residencies. For example, this is the means by which many dermatologists have learned laser surgery and surgeons laparoscopic cholecystectomy. It is also the way in which all specialists who' completed residencies before 1982 have learned liposuction. These educational channels for the postgraduate acquisition ofnew skills and competence are commonly used and are an important
Correspondence 315 process to allow physicians to grow in knowledge and abilities beyond those that were available or taught in residency. It is clear, however, that these new capabilities are more readily and proficiently acquired if the founda tion for them is part of residency training. This founda tion for dermatologic surgery is being achieved currently in dermatology residencies and is reinforced and sup ported by the new special requirements for dermatology. In summary, there is strong support and agreement for Dr. Jones' position on the need to maintain excellence in the basic, laboratory, and clinical sciences in dermatology residency. The new special requirements for dermatology are additional provisions, not substitutions, thatreflect the current educational practice in the vast majority of resi dency training programs. Thus they are the results of ev olutionary changes in our specialty, not the whims of a surgical minority. These acknowledge by organized med icine that dermatology is a medical and surgical specialty. These developments present special challenges and offer notable opportunities for our specialty. E. A. Krull, MD Department of Dermatology Henry Ford Hospital 2799 W. Grand Blvd. Detroit, MI48202-2689 REFERENCE
1. Tromovitch TA, Stegman SJ. Microscopically controlled excision of skin tumors. Arch Dermatol 1974;110:231.
Photoagingjphotodamage and photoprotection To the Editor: We read with interest the CME article by Taylor, Stern, Leyden, and Gilchrest (J AM ACAD DER· MATOL 1990;22;1-15). Because it is important to provide the most accurate and current information in continuing education articles, we haveseveral specific comments that differ with some ofthe information reported, and we be lieve they will be of interest to the dermatologic commu nity. Ample data now exist to show that para-aminobenzoic acid (PABA) does not bind to proteins to give "protection even after bathing, swimming, or perspiring" as the arti cle reports. PABA crystallizes on the skin's surface and is vulnerable to removal by water after as little as 10 min utes of water exposure.1-6 The proposed Food and Drug Administration (FDA) standard test for waterproofprod ucts is 80 minutes of water exposure. If a product is wa terproof by this standard, it may also claim to be sweat resistant. The Bonin and Gallagher work7• 8 that purported to demonstrate mutagenic and tumor-promoting properties of 2-ethylhexyl p-methoxycinnamate has been refuted. Extensive safety testing has demonstrated that the earlier
316
Journal of the American Academy of Dermatology
Correspondence
work was in error and that this sunscreen is not mutagenic or carcinogenic. 9. 12 Readers should be aware ofthese im portant studies because more and more commercial products contain the ingredient in question. Although the article by Taylor et al. maintains that a 2D-minute to 2-hour delay after sunscreen application and before sun exposure "is probably optimal," we are not aware of data to support a 2-hour delay other than in old publications on PABA in alcohol. 13 ,14 Currently mar keted sunscreen products are effective when initially ap plied. Although it is important to let a waterproof prod uct dry before water immersion to minimize wash-off, many consumers apply their sunscreen on the beach. We know of no data to support the idea that the efficacy of currently available products increases with time after ap plication. The statement that there are no standards for defining light source, skin type, and quantity of sunscreen for test ing the efficacy of sunscreens is surprising; all these topics are addressed in the 1978 FDA over-the-counter monograph. IS The sun protection factor (SPF) values that appear on the labels of U.S. products are generally valid if the user follows the detailed procedure set forth by the FDA in this document. We realize that the issue of international standards has not yet been resolved, but progress continues in this area. The 1982 Pathak article on outdoor testing J6 cited by Taylor et al. was updated in 1986 to include test results on many sunscreens in the ultra protection category (SPF 15 and higher), and it was found that their SPFs remained similar in indoor and outdoor tests. 17 Recent studies of commercial waterproof products with high SPFs have shown that their SPFs are similar indoors and outdoors and that they maintain their efficacy after swimming (M. Pathak and R. Sayre, manuscript in preparation). The life-table analysis method J8 for assigning the pro tection value of sunscreens has been criticized as imprac tical and imprecise. It requires up to 20 individual UV exposures over several days. If minimal erythema is not found atone ofthe given exposures, the minimal erythema dose (MED) is estimated. For products with no deter mined MED, an MED value is "assigned." This test pro cedure has not met with acceptance because it does not result in a defined, reproducible value. One article is cited to support the assertion that the amount of sunscreen usually applied is "probably less than half that recommended." Several other references indicate that, although the amount that is used varies, it is probably at or greater than 2 mg/cm2.19-23 At any rate, the amount used for SPF determination (2 mg/cm2) is just enough to cover the test site evenly and completely. Use of less would make the test result unreliable because of uneven spreading and would make product compari sons meaningless. 19, 23 The issue of application density has proved to be par ticularly troublesome for international standardization.
We are glad to report that the Commission Internation ale de L'Eclairage (CIE) has recently adopted 2 mg/cm2 as the appropriate application density in its guidelines. 24 Because we realize the importance of presenting the most up-to-date information, we hope you will print this letter soon as an update to your previous article.
Patricia Agin, PhD Schering-Plough Health Care Products 3030 Jackson Ave. Memphis, TN 38151 REFERENCES 1. Morasso MI, Thielemann AM, Pinto C, et ai. In vitro and in vivo study of the substantivity of p-aminobenzoic acid and two of its esters. J Soc Cosmet Chern 1985;36:355-62. 2. LeVee GJ, Sayre RM, Marlowe E. P-aminobenzoic acid as a sunscreen and its behavior on skin. Int J Cosmet Sci 1981;3:49-55. 3. Sayre RM, Marlowe E, Agin PP, et ai. Performance of six sunscreens on human skin. Arch Dermatol 1979;115:46-9. 4. Kaidbey KH, Kligman AM. An appraisal of the efficacy and substantivity ofthe new high-potency sunscreens. J AM ACAD DERMATOL 1981;4:566-70. 5. Pathak MA, Fitzpatrick TB, Greiter FJ, et aI. Principles of photoprotection in sunburn and tanning, and topical and systemic photoprotection in health and disease. J Dermatol Surg Oneal 1985;11:575-9. 6. Blank IB, Cohen JH, Anderson RR, et ai. Observations on the mechanism of the protective action of sunscreens. J In vest Dermatol 1982;78:381-5. 7. Bonin AM, Arlauskas AP, Angus DS, et al. UV-absorbing and other sun-protecting substances: genotoxicity of2-eth ylhexyl p-methoxycinnamate. Mutat Res 1982;105:303-8. 8. Gallagher CH, Greenoak GE, Reeve VE, et aI. Ultraviolet carcinogenesis in the hairless mouse skin: influence of the sunscreen 2-ethylhexyl methoxycinnamate. Aust J Exp BioI Med Sci 1984;62:577-88. 9. Baker RSU, Gallagher CH, Lane Brown MM. Sunscreen not mutagenic. Med J Aust 1980;2:284. 10. National Toxicology Program, U.S. Dept. of Health and Human Services, Technical Bulletin No.9, 1983. 11. Roche Research Reports Nos. 93336, 104840, 105032, 104902, 105005, 105024, 104916, Hoffman LaRoche! Givaudan Corp. 12. Forbes D, Davies RE, Sambuco CP, et al. Inhibition of so lar UVR-induced skin tumors in hairless mice by topical application of sunscreens. Report to The Givaudan Corpo ration, 1987. 13. Algra RJ, Knox JM. Topical photoprotectivc agents. Int J Dermatol 1978;17:628-34. 14. Pathak MA, Fitzpatrick TB, Frenk E. Evaluation of topi cal agents that prevent sunburn: the superiority of PABA and its esters in ethyl alcohoI. NEnglJ Med 1969;280:1459 63. 15. Department of Health, Education, and Welfare, Food and Drug Administration. Sunscreen drug products for over the counter human use. Fed Reg Aug. 25,1978;43:38206-9. 16. Pathak MA. Sunscreens: topical and systemic approaches for protection of human skin against harmful effects of so lar radiation. JAM ACAD DERMATOL 1982;7:285-312. 17. Pathak MA. Topical and systemic approaches for the pre vention of acute and chronic sun-induced reactions. Derm Clin 1986;4:321-34.
Volume 24 Number 2, Part 1 February 1991 18. Azizi E, Modan M, Kushelevsky AP, et al. A more reliable index of sunscreen protection based on life-table analysis of individual sun protection factors. Br J Dermatol 1987; 116:693-702. 19. Sayre RM. Sunscreen application: flawed study. Arch DermatoI1986;122:745. 20. Wiskemann A. Zur reproduzierbarkeit des lichtschutzfac tors. Fette Seifen Anstrichmittel 1968;70:361-4. 21. Hoppe U. Photostabilitat und hautaffinitat. J Soc Cosmet Chern. 1974;25:667-80. 22. Hoppe U. Factors determining the effectiveness of sun screening agents. Cosmet Sci 1980;2:147-9. 23. Schlagel CA, Sanborn EM. Weights of topical prepara tions required for total and partial body inunction. J Invest DermatoI1964;42:253-6. 24. CIE Photobiology and photochemistry technical committee division 6 TC12 final report: phototesting ofskin application for sun protection. September 1989.
Reply To the Editor: We thank Dr. Agin for her comments from the perspective of one directly involved in sunscreen development and evaluation. We wish to add only a few more comments from the perspective of physicians at tempting to interpret this now formidable literature for the benefit of their patients and colleagues. We are unaware of the ample data cited in Dr. Agin's unreferenced statement that para-aminobenzoic acid (PABA) does not undergo hydrogen binding to stratum corneum proteins and that PABA cannot provide some protection after bathing, swimming, or perspiring, as we stated in our article. We certainly did not mean to imply that PABA has high substantivity. Many other sunscreen ingredients are far superior in this regard, and sun· screens containing them are correctly advertised as "waterproof," whereas sunscreens containing PABA alone are not. With regard to the possible mutagenicity of 2-ethyl hexyl p-methoxycinnamate, of the four articles cited by Dr. Agin as refuting the works of Bonin, Gallagher, and their co-workers, the first article (for which Dr. Gallagher is a co-author) preceded the two positive studies, and the remaining three articles are unfortunately unavailable for all practical purposes to the medical community. We would encourage Dr. Agin and others with access to these data to publish a thorough and critical review of the mu tagenicity of all suspect sunscreen ingredients in a more accessible journal. With regard to the "optimal" period between applica tion of a sunscreen and exposure to the sun, it must be noted that ifthe user delays application until comfortably settled on the beach, he or she will probably receive more UV irradiation in transit, before the sunscreen is applied, than in the remainder of the day after an effective sunscreen has been applied. For this reason alone, we urge sunscreen manufacturers and physicians to recommend application of sunscreen well in advance of the intended sun exposure.
Correspondem:e 317 Although standards for light source, skin type, and quantity. of sunscreen were proposed . in a 1978 FDA monograph, they have also been addressed subsequently by several FDA"organized panels and argued by inter ested parties in a variety of formal and informal settingS. This continuing discussion suggests to us that neither the FDA nor the medical arid scientific communities are united in their recommendations. Surely the existence of FDA guidelines does not imply unanimity of opinion re garding the ideal sunscreen testing procedure. Weapologizefor having failed toreference Dr. Pathak's 1986 review. Our article does, however, note that indoor and outdoor SPFs tend to be similar for substantive sun screens, precisely Dr. Agin's point. With regard to the life-table analysis method for assigning a protection value to sunscreens, we agree that it has inherent difficulties. Our point is only that all methods have their difficulties. The amount of sunscreen applied by the average user is probably best considered to be unknown. However, of the four papers cited by Dr. Agin to indicate that it is greater than the 2 mgjcm2 used in SPF testing, one is a letter by Dr. Agin's co-worker criticiziIig the study we cited but providing no refuting data, and the other three are again essentially unavailable, although the titles sug gest that the amount of sunscreen spontaneously applied by casual users was not studied. Dr. Agin's related point, that SPF testing with less than 2 mgjcm2 of sunscreen would yield unreliable results, is irrelevant to the concern that many consumers apparently use sunscreens in this way and thus achieve far less protection than they assume. The elegant and effective sunscreens now available are testimony to the dedication and biochemical sophisti~a tion of the sunscreen industry, and they greatly facilitate the dermatologist's task of encouraging enlightened pre ventive health practices by the public. We concur com pletely with Dr. Agin that up-ta-date information regard ing these sunscreens should be readily available to dermatologists and to the public.
Barbara A. Gilchrest, MD,a Robert S. Stern, MD,b and Charles R. Taylor; MU Human Nutrition Research Center on Aging at Tufts University and Department ofDermatology, Boston University Medical School,a and Department of Dermatology, Beth Israel Hospital, Harvard Medical School,b Boston, Massachusetts
Athlete's nodules To the Editor: "Surfer's nodules" were one of the sports medicine-related injuries discussed in Dr. Basler's excel lent review of injury-induced cutaneous conditions assa ciatedwith athletic participation (J AM ACAO DERMA TOL 1989;21:1257-62). We recently described a 54-year