- Email: [email protected]
Skin Tests in the Diagnosis of Allergies of the Immediate Type
Symposium on Allergy in Adults
Skin Tests in the Diagnosis of Allergies of the Immediate Type Raymond G. Slavin, M.D.*
It is just over 100 years since Blackley first described the allergen-induced wheal and erythema skin response as a useful diagnostic procepatients."2 The fact that skin testing is still in widespread dure in atopic patients. use is evidence enough that it has withstood the test of time as a basic tool of the allergist. On its centennial anniversary, it seems particularly appropriate to examine once more the usefulness of the immediate wheal and erythema skin test, especially in light of the recent development of newer in vivo and in vitro diagnostic tests. The immediate skin test reaction is due to the interaction between antigen and IgE skin-sensitizing antibody bound to tissue mast cells. The skin test procedure must deliver an appropriate amount of aqueous antigen beneath the stratum corneum and the barrier zone of the epidermis in order to combine with the tissue mast cell. The IgE molecule has a particular affinity for mast cells and basophils. The affinity is based on two inherent features. First, the Fc portion of the IgE molecule contains the structures essential for attachment to the cell sites. Second, the receptor sites of the cell are surface structures on the plasma membrane capable of binding the Fc portion of the IgE molecule. The only immunoglobulin present in significant amounts on basophils and mast cells is IgE. It is estimated that between 30,000 and 100,000 receptor sites are located on 10 each mast cell. 10 Two IgE molecules are required for the formation of skin-reactive complexes. One antigen molecule must bridge or combine with at least two antibody molecules on the cell to be effective in vivo. When the combination of one antigen and two antibody molecules occurs, there is an allosteric phenomenon probably involving structural changes in the IgE antibody molecule. This affects the cell membrane so as to result in the liberation from the cell of mediator substances, most notably histamine. These mediators cause local vasodilatation and increased ':'Professor of Internal Medicine, and Director, Section of Allergy and Immunology, Se St. Louis University School of Medicine, St. Louis, Missouri
AmericaMedical Clinics of North America - Vo!. 58, No. 1, January 1974
65
66
RAYMOND
G.
SLAVIN
capillary permeability resulting in the positive wheal and erythema reaction. It is not the purpose of this chapter to discuss the technical aspects of allergen preparation or the various skin test procedures and their advantages and disadvantages. Instead we will devote our attention to some of the common misconceptions of skin testing and the fallacies of both the positive and negative skin test.
Fallacies of the Positive Skin Test - The "False-Positive" Skin Test Improper Preparation and Administration of the Allergen Solu13 tion. 13 Skin testing is performed with an aqueous solution of the antigen prepared by extracting the appropriate allergenic material with buffered saline. Many factors may contribute to producing a skin testing solution which is nonspecifically irritating. Deviation from a physiologic pH or proper osmolarity will cause a false-positive skin test. Many extracts, particularly foods, house dust, and feathers, contain irritants of low molecular weight and it is necessary to dialyze these materials befor utilizing them as skin testing agents. Glycerine, commonly used as a preservative in allergy extracts, will cause nonspecific irritation at a concentration of 6 per cent if injected intradermally. Injecting too large a volume of extract intradermally will also cause false-positive reactions. The optimal volml. ume is 0.02 m!. Nonspecifically Release Histamine or Contain Substances Which Nonspecijically Histamine Themselves. Materials which are urticariogenic will cause a wheal and erythema skin test response in all subjects. Example are morphine and codeine. Some food extracts, particularly cheeses, have high histamine content and will cause false-positive reactions. 44 Dermographic Subjects. It is estimated that dermographism is present in 5 to 20 per cent of the population, depending on the degree of ll pressureY pressure. Skin testing should always include a saline control to insure that one is not dealing with a dermographic subject. A Remnant of Past Sensitivity. It is not common to find positive skin test reactivity persisting in an individual whose clinical sensitivity has disappeared. A Harbinger of Future Sensitivity. The onset of the clinical symptoms of allergic rhinitis is generally preceded by a positive pollen scratch test. Hagy and Settipane 77 found that the frequency of new hay fever developing in college seniors who had no clinical manifestations of allergy velopirg fre$hmen is more than 10 times higher in students with initial positive as freshmen pollen scratch tests than in students with no positive pollen scratch tests. Individuals with 2 plus or greater skin tests developed hay fever more than 13 times greater than negative pollen reactors. Thus, the risk of developing an allergic condition is considerably greater in individuals with a positive skin test. Dissociation of Positive Skin Reactivity and Clinical Sensitivity. Perhaps the most important reason for the false-positive skin test is the physician's failure to realize that a positive skin test reaction is not necessarily an indicator of clinical sensitivity. IgE allergic antibody is not always fixed in both the patient's skin and the allergic shock organ. Therefore, the simple presence of a positive skin test does not insure that
SKIN TESTS IN THE DIAGNOSIS OF ALLERGIES OF THE IMMEDIATE TYPE
67
the allergic antibody is also fixed to the conjunctiva, the nose, or the bronchial tree. Special mention should be made of skin tests for reactivity to foods. It is here that there is the widest discrepancy between skin reactivity and clinical sensitivity. It has been estimated that only 20 per cent of skin tests positive for certain foods have a positive clinical correlation. correlationY9 The best correlation is found in patients who develop symptoms immediately after ingestion of a food. The correlation is much less when the onset of symptoms is delayed. The patient may show a positive skin test for the undigested food but may be nonallergic to digestive breakdown products. More will be mentioned later on the subject of the anti antigenic genic changes in foods caused by digestion.
The Fallacies of the Negative Skin Test - The "False-Negative" Skin TestTest Improper Preparation and Administration of the Allergen Solution. Allergy extracts lose potency with storage. Therefore, outdated extracts will give a false-negative reaction. One has to be sure that the extraction procedure was long enough and carried out with the correct buffer to insure that the allergenic material is indeed present in the solution. In addition, the appropriate material must be used as the initial source of allergen. An example is the proper preparation of dog or cat extract. Animal hair or fur is practically devoid of soluble antigen. Therefore, extraction of dog hair clipped from the animal will contain little antigen. In order to prepare a proper allergen solution of dog, the skin or dander, which can readily be obtained by brisk brushing of the animal, must be used. As stated earlier, the allergen solution must penetrate the stratum corneum and barrier zone of the epidermis in order to combine with the tissue mast cells. Too superficial a scratch or prick of the skin will not deliver an adequate amount of allergen solution to the mast cells. Inherent Host Factors. The age of the subject to be tested must be considered in evaluating a negative skin test response. The skin of young infants and very elderly patients will yield smaller skin test reactions. Other host factors affecting skin test response include the temperature of the skin and the integrity of the autonomic innervation of cutaneous vessels. The Refractory Period After an Anaphylactic Reaction. Shortly after a severe systemic reaction to an allergen, the patient may enter a refractory period because of exhaustion of the skin-sensitizing antibody, Skin testing during this period may yield a false-negative response. It is necessary to wait 2 weeks after a systemic reaction to, for example, an insect sting before one can accurately skin test an individual with stinging insect antigen. Negative Skin Test Reactions to Food. As noted earlier, there is a poor correlation between skin test reactivity to foods and clinical sensitiv14 ity. Spies et al. have recently reported studies that may explain why paal,14 tients may have a negative skin test reaction to a particular food and yet have an allergic response on ingesting that food. They simulated stomach digestion by subjecting B-Iactoglobulin to 6 successive 8 minute pepsin
68
RAYMOND
G.
SLAVIN
hydrolyses. These procedures resulted in the formation of 8 new antigens B-lactoglobulin. Therefore, a patient quite different from the original B-Iactoglobulin. may be nonreactive to the original food but could respond to new antigens formed by the digestive process. Negative Skin Test Reactions to Drugs. Many diagnostic and therapeutic agents will not elicit a positive skin test reaction although they will cause serious systemic reactions in sensitive individuals with ordinary use. Examples include local anesthetics, aspirin, and radiopaque dyes. It is imperative that the physician not be misled by a negative skin reaction in such situations. Glib administration of the agent may result in a life-threatening reaction. Drug sensitivity may often be due to an immunogenic hapten protein conjugate formed by a metabolic product of the drug in combination with a tissue protein. Skin testing with the drug alone would obviously result in a negative reaction. Drugs Which Inhibit the Skin Test Reaction. There is great misunderstanding about medications which inhibit immediate skin test reactivity. The error is generally in attributing inhibitory properties to agents which do not in fact possess such a property. It is, however, important to consider a negative skin test response in terms of possible inhibiting drugs. Most authors have concluded that corticosteroids have no effect on the immediate skin test response. response:"5 ,66 This is in contrast to the markedly inhibiting effect that it has on cell-mediated immunity or the delayed hypersensitivity tuberculin-like reaction. There is one report of triamcinolone given over a 3 day period significantly inhibiting allergen-induced skin reaction. HH al. 66 have demonstrated that neither ephedrine nor aminoGalant et a1. phylline given by clinically useful routes and in the usual dosage causes significant inhibition of histamine or allergen induced wheal and flare reactions. The question of the inhibitory effect of these two drugs in combination is not settled. Subcutaneous epinephrine appears to cause a short term inhibition l2 Isoproterenol is weakly inhibitory of the of the wheal and flare reaction. 12 12 allergen induced skin test by the sublingual but not by the aerosol route. 12 Antihistamines have been known for many years to inhibit immediate skin reactivity.l The most potent inhibitor of this group is hydroxyzine which, given over a 24 hour period, significantly inhibits the skin test reaction for at least 24 hours after the last dose. GG Antihistamines should be discontinued at least 24 to 48 hours before skin testing. Recent evidence indicates that there are significant individual differences in patients' ability to metabolize antihistamines. antihistaminesY3
CONCLUSION Much attention has been given in this article to the potential fallacies of skin tests in the diagnosis of allergies of the immediate type. Yet after 100 years, skin tests are still a valuable diagnostic tool for the allergist. It is essential, however, to avoid the pitfall of placing too much emphasis on
SKIN TESTS IN THE DIAGNOSIS OF ALLERGIES OF THE IMMEDIATE TYPE
69
either the positive or negative skin test. No test, whether in vivo or in vitro, old or newly developed, provides the final diagnosis. To hand the patient a list of inhalants and foods to which he or she is "allergic" based solely on positive skin tests is indefensible. The physician needs a thorough knowledge of his patient. Any diagnostic test, including skin testing, must be interpreted in the clinical light, in terms of the history and physical examination.
REFERENCES 1. Arbesman, C. E., Loepf, G. F., and Miller, G. E.: Some antianaphylactic and antihistamine properties of N'pyridyl, N'bensyl, demethylethylenediomine monohydrochloride. J. Allergy, 1 7: 203, 1946. 2. Blackley, C. H.: Experimental Researches on the Causes and Nature of Catarrhus Aestivxus (Hay Fever and Asthma). London, Bailliere, Tindall, and Cox, 1873. Mac Queen, D. M., Wittig, H. J., et al. Degree and duration of skin test suppres3. Cook, T. J., MacQueen, sion and side effects with antihistamine. J. Allerg. Clin. Immun., 51 :71, 1973. 4. Doeglas, H. M. G., and Nater, J. P.: Histamine in foods causing false-positive scratch tests. J. Allergy, 42:164,1968. 5. Feinberg, S. M., Dannenberg, T. B., and Malkiel, S.: ACTH and cortisone in allergic 22:195,1951. manifestations. J. Allergy, 22:195, 1951. aL: The inhibitor effect of antiallergy drugs on 6. Galant, S. P., Bullock, J., Wong, D., et al.: 51 : 11, allergen and histamine induced wheal and flare response. J. Allerg. Clin. Immun., 51: 1973. 7. Hagy, G. W., and Settipane, G. A.: Prognosis of positive allergy skin tests in an asymptomatic population. J. Allerg. Clin. Immun., 48:200, 1971. 8. Haugh, H. E., and Vale, J. R.: The influence of triamcinolone on the allergic skin wheal re20:496, action. Acta Allergol., 20 :496, 1965. 9. Hill, L. W.: Food sensitivity in 100 asthmatic children. New Eng. J. Med., 238:657, 1948. ofIgE 10. Ishizaka, T., Soto, C. S., and Ishizaka, K.: Binding of IgE molecules on human basophils. J. 51 :79,1973. 79, 1973. Allerg. Clin. Immun., 51: 11. Johnson, T. J., and Cazort, A. G.: Dermographia-Clinical observations. J. A. M. A., 169:23, 1959. 12. Sheldon, J. M., and Lovell, R. G.: Effect of isuprel on antigen antibody and histamine skin reactions. Ann. Allergy, 9:45, 1951. 13. Sheldon, J. M., Lovell, R. G., and Mathews, K. P.: A Manual of Clinical Allergy. Philadelphia, W. B. Saunders Co., 1967, Appendix 1, pp. 507-532. 14. Spies, J. R., Stevan, M. A., and Stein, W. J.: The chemistry of allergens. XXI. 8 new antiB-lactoglobulin. J. Allerg. gens generated by successive pepsin hydrolyses of bovine B-Iactoglobulin. 1172. Clin. Immun., 50:82, 11 72. 15. Tuft, L., and Brodsky, M. L.: The influence of various drugs upon allergic reaction. J. 7: 238, 1936. Allergy, 7:238,
Section of Allergy and Immunology St. Louis University School of Medicine St. Louis, Missouri 63104
Skin Tests in the Diagnosis of Allergies of the Immediate Type Raymond G. Slavin, M.D.*
It is just over 100 years since Blackley first described the allergen-induced wheal and erythema skin response as a useful diagnostic procepatients."2 The fact that skin testing is still in widespread dure in atopic patients. use is evidence enough that it has withstood the test of time as a basic tool of the allergist. On its centennial anniversary, it seems particularly appropriate to examine once more the usefulness of the immediate wheal and erythema skin test, especially in light of the recent development of newer in vivo and in vitro diagnostic tests. The immediate skin test reaction is due to the interaction between antigen and IgE skin-sensitizing antibody bound to tissue mast cells. The skin test procedure must deliver an appropriate amount of aqueous antigen beneath the stratum corneum and the barrier zone of the epidermis in order to combine with the tissue mast cell. The IgE molecule has a particular affinity for mast cells and basophils. The affinity is based on two inherent features. First, the Fc portion of the IgE molecule contains the structures essential for attachment to the cell sites. Second, the receptor sites of the cell are surface structures on the plasma membrane capable of binding the Fc portion of the IgE molecule. The only immunoglobulin present in significant amounts on basophils and mast cells is IgE. It is estimated that between 30,000 and 100,000 receptor sites are located on 10 each mast cell. 10 Two IgE molecules are required for the formation of skin-reactive complexes. One antigen molecule must bridge or combine with at least two antibody molecules on the cell to be effective in vivo. When the combination of one antigen and two antibody molecules occurs, there is an allosteric phenomenon probably involving structural changes in the IgE antibody molecule. This affects the cell membrane so as to result in the liberation from the cell of mediator substances, most notably histamine. These mediators cause local vasodilatation and increased ':'Professor of Internal Medicine, and Director, Section of Allergy and Immunology, Se St. Louis University School of Medicine, St. Louis, Missouri
AmericaMedical Clinics of North America - Vo!. 58, No. 1, January 1974
65
66
RAYMOND
G.
SLAVIN
capillary permeability resulting in the positive wheal and erythema reaction. It is not the purpose of this chapter to discuss the technical aspects of allergen preparation or the various skin test procedures and their advantages and disadvantages. Instead we will devote our attention to some of the common misconceptions of skin testing and the fallacies of both the positive and negative skin test.
Fallacies of the Positive Skin Test - The "False-Positive" Skin Test Improper Preparation and Administration of the Allergen Solu13 tion. 13 Skin testing is performed with an aqueous solution of the antigen prepared by extracting the appropriate allergenic material with buffered saline. Many factors may contribute to producing a skin testing solution which is nonspecifically irritating. Deviation from a physiologic pH or proper osmolarity will cause a false-positive skin test. Many extracts, particularly foods, house dust, and feathers, contain irritants of low molecular weight and it is necessary to dialyze these materials befor utilizing them as skin testing agents. Glycerine, commonly used as a preservative in allergy extracts, will cause nonspecific irritation at a concentration of 6 per cent if injected intradermally. Injecting too large a volume of extract intradermally will also cause false-positive reactions. The optimal volml. ume is 0.02 m!. Nonspecifically Release Histamine or Contain Substances Which Nonspecijically Histamine Themselves. Materials which are urticariogenic will cause a wheal and erythema skin test response in all subjects. Example are morphine and codeine. Some food extracts, particularly cheeses, have high histamine content and will cause false-positive reactions. 44 Dermographic Subjects. It is estimated that dermographism is present in 5 to 20 per cent of the population, depending on the degree of ll pressureY pressure. Skin testing should always include a saline control to insure that one is not dealing with a dermographic subject. A Remnant of Past Sensitivity. It is not common to find positive skin test reactivity persisting in an individual whose clinical sensitivity has disappeared. A Harbinger of Future Sensitivity. The onset of the clinical symptoms of allergic rhinitis is generally preceded by a positive pollen scratch test. Hagy and Settipane 77 found that the frequency of new hay fever developing in college seniors who had no clinical manifestations of allergy velopirg fre$hmen is more than 10 times higher in students with initial positive as freshmen pollen scratch tests than in students with no positive pollen scratch tests. Individuals with 2 plus or greater skin tests developed hay fever more than 13 times greater than negative pollen reactors. Thus, the risk of developing an allergic condition is considerably greater in individuals with a positive skin test. Dissociation of Positive Skin Reactivity and Clinical Sensitivity. Perhaps the most important reason for the false-positive skin test is the physician's failure to realize that a positive skin test reaction is not necessarily an indicator of clinical sensitivity. IgE allergic antibody is not always fixed in both the patient's skin and the allergic shock organ. Therefore, the simple presence of a positive skin test does not insure that
SKIN TESTS IN THE DIAGNOSIS OF ALLERGIES OF THE IMMEDIATE TYPE
67
the allergic antibody is also fixed to the conjunctiva, the nose, or the bronchial tree. Special mention should be made of skin tests for reactivity to foods. It is here that there is the widest discrepancy between skin reactivity and clinical sensitivity. It has been estimated that only 20 per cent of skin tests positive for certain foods have a positive clinical correlation. correlationY9 The best correlation is found in patients who develop symptoms immediately after ingestion of a food. The correlation is much less when the onset of symptoms is delayed. The patient may show a positive skin test for the undigested food but may be nonallergic to digestive breakdown products. More will be mentioned later on the subject of the anti antigenic genic changes in foods caused by digestion.
The Fallacies of the Negative Skin Test - The "False-Negative" Skin TestTest Improper Preparation and Administration of the Allergen Solution. Allergy extracts lose potency with storage. Therefore, outdated extracts will give a false-negative reaction. One has to be sure that the extraction procedure was long enough and carried out with the correct buffer to insure that the allergenic material is indeed present in the solution. In addition, the appropriate material must be used as the initial source of allergen. An example is the proper preparation of dog or cat extract. Animal hair or fur is practically devoid of soluble antigen. Therefore, extraction of dog hair clipped from the animal will contain little antigen. In order to prepare a proper allergen solution of dog, the skin or dander, which can readily be obtained by brisk brushing of the animal, must be used. As stated earlier, the allergen solution must penetrate the stratum corneum and barrier zone of the epidermis in order to combine with the tissue mast cells. Too superficial a scratch or prick of the skin will not deliver an adequate amount of allergen solution to the mast cells. Inherent Host Factors. The age of the subject to be tested must be considered in evaluating a negative skin test response. The skin of young infants and very elderly patients will yield smaller skin test reactions. Other host factors affecting skin test response include the temperature of the skin and the integrity of the autonomic innervation of cutaneous vessels. The Refractory Period After an Anaphylactic Reaction. Shortly after a severe systemic reaction to an allergen, the patient may enter a refractory period because of exhaustion of the skin-sensitizing antibody, Skin testing during this period may yield a false-negative response. It is necessary to wait 2 weeks after a systemic reaction to, for example, an insect sting before one can accurately skin test an individual with stinging insect antigen. Negative Skin Test Reactions to Food. As noted earlier, there is a poor correlation between skin test reactivity to foods and clinical sensitiv14 ity. Spies et al. have recently reported studies that may explain why paal,14 tients may have a negative skin test reaction to a particular food and yet have an allergic response on ingesting that food. They simulated stomach digestion by subjecting B-Iactoglobulin to 6 successive 8 minute pepsin
68
RAYMOND
G.
SLAVIN
hydrolyses. These procedures resulted in the formation of 8 new antigens B-lactoglobulin. Therefore, a patient quite different from the original B-Iactoglobulin. may be nonreactive to the original food but could respond to new antigens formed by the digestive process. Negative Skin Test Reactions to Drugs. Many diagnostic and therapeutic agents will not elicit a positive skin test reaction although they will cause serious systemic reactions in sensitive individuals with ordinary use. Examples include local anesthetics, aspirin, and radiopaque dyes. It is imperative that the physician not be misled by a negative skin reaction in such situations. Glib administration of the agent may result in a life-threatening reaction. Drug sensitivity may often be due to an immunogenic hapten protein conjugate formed by a metabolic product of the drug in combination with a tissue protein. Skin testing with the drug alone would obviously result in a negative reaction. Drugs Which Inhibit the Skin Test Reaction. There is great misunderstanding about medications which inhibit immediate skin test reactivity. The error is generally in attributing inhibitory properties to agents which do not in fact possess such a property. It is, however, important to consider a negative skin test response in terms of possible inhibiting drugs. Most authors have concluded that corticosteroids have no effect on the immediate skin test response. response:"5 ,66 This is in contrast to the markedly inhibiting effect that it has on cell-mediated immunity or the delayed hypersensitivity tuberculin-like reaction. There is one report of triamcinolone given over a 3 day period significantly inhibiting allergen-induced skin reaction. HH al. 66 have demonstrated that neither ephedrine nor aminoGalant et a1. phylline given by clinically useful routes and in the usual dosage causes significant inhibition of histamine or allergen induced wheal and flare reactions. The question of the inhibitory effect of these two drugs in combination is not settled. Subcutaneous epinephrine appears to cause a short term inhibition l2 Isoproterenol is weakly inhibitory of the of the wheal and flare reaction. 12 12 allergen induced skin test by the sublingual but not by the aerosol route. 12 Antihistamines have been known for many years to inhibit immediate skin reactivity.l The most potent inhibitor of this group is hydroxyzine which, given over a 24 hour period, significantly inhibits the skin test reaction for at least 24 hours after the last dose. GG Antihistamines should be discontinued at least 24 to 48 hours before skin testing. Recent evidence indicates that there are significant individual differences in patients' ability to metabolize antihistamines. antihistaminesY3
CONCLUSION Much attention has been given in this article to the potential fallacies of skin tests in the diagnosis of allergies of the immediate type. Yet after 100 years, skin tests are still a valuable diagnostic tool for the allergist. It is essential, however, to avoid the pitfall of placing too much emphasis on
SKIN TESTS IN THE DIAGNOSIS OF ALLERGIES OF THE IMMEDIATE TYPE
69
either the positive or negative skin test. No test, whether in vivo or in vitro, old or newly developed, provides the final diagnosis. To hand the patient a list of inhalants and foods to which he or she is "allergic" based solely on positive skin tests is indefensible. The physician needs a thorough knowledge of his patient. Any diagnostic test, including skin testing, must be interpreted in the clinical light, in terms of the history and physical examination.
REFERENCES 1. Arbesman, C. E., Loepf, G. F., and Miller, G. E.: Some antianaphylactic and antihistamine properties of N'pyridyl, N'bensyl, demethylethylenediomine monohydrochloride. J. Allergy, 1 7: 203, 1946. 2. Blackley, C. H.: Experimental Researches on the Causes and Nature of Catarrhus Aestivxus (Hay Fever and Asthma). London, Bailliere, Tindall, and Cox, 1873. Mac Queen, D. M., Wittig, H. J., et al. Degree and duration of skin test suppres3. Cook, T. J., MacQueen, sion and side effects with antihistamine. J. Allerg. Clin. Immun., 51 :71, 1973. 4. Doeglas, H. M. G., and Nater, J. P.: Histamine in foods causing false-positive scratch tests. J. Allergy, 42:164,1968. 5. Feinberg, S. M., Dannenberg, T. B., and Malkiel, S.: ACTH and cortisone in allergic 22:195,1951. manifestations. J. Allergy, 22:195, 1951. aL: The inhibitor effect of antiallergy drugs on 6. Galant, S. P., Bullock, J., Wong, D., et al.: 51 : 11, allergen and histamine induced wheal and flare response. J. Allerg. Clin. Immun., 51: 1973. 7. Hagy, G. W., and Settipane, G. A.: Prognosis of positive allergy skin tests in an asymptomatic population. J. Allerg. Clin. Immun., 48:200, 1971. 8. Haugh, H. E., and Vale, J. R.: The influence of triamcinolone on the allergic skin wheal re20:496, action. Acta Allergol., 20 :496, 1965. 9. Hill, L. W.: Food sensitivity in 100 asthmatic children. New Eng. J. Med., 238:657, 1948. ofIgE 10. Ishizaka, T., Soto, C. S., and Ishizaka, K.: Binding of IgE molecules on human basophils. J. 51 :79,1973. 79, 1973. Allerg. Clin. Immun., 51: 11. Johnson, T. J., and Cazort, A. G.: Dermographia-Clinical observations. J. A. M. A., 169:23, 1959. 12. Sheldon, J. M., and Lovell, R. G.: Effect of isuprel on antigen antibody and histamine skin reactions. Ann. Allergy, 9:45, 1951. 13. Sheldon, J. M., Lovell, R. G., and Mathews, K. P.: A Manual of Clinical Allergy. Philadelphia, W. B. Saunders Co., 1967, Appendix 1, pp. 507-532. 14. Spies, J. R., Stevan, M. A., and Stein, W. J.: The chemistry of allergens. XXI. 8 new antiB-lactoglobulin. J. Allerg. gens generated by successive pepsin hydrolyses of bovine B-Iactoglobulin. 1172. Clin. Immun., 50:82, 11 72. 15. Tuft, L., and Brodsky, M. L.: The influence of various drugs upon allergic reaction. J. 7: 238, 1936. Allergy, 7:238,
Section of Allergy and Immunology St. Louis University School of Medicine St. Louis, Missouri 63104