156 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS A recent study by Schorr et al. (5) emphasizes reproducibility of test re- sults and convincingly separates neomycin reactors from nonreactors. How- ever, regretably, it d.oes not establish the nature of the process or processes that are responsible for the dermal reactivity. Within the patient population, neomycin dermatoses, as well as the skin tests for establishing them, may be the result of histamine release due to a chemical irritation rather than an allergic phenomenon. A noteworthy report which helps to purge neomycin of its onus considers the vehicle in which neomycin is presented to skin, suggesting that pene- trability through the epidermis is an important factor. Hjorth (6) in his 1968 review of neomycin reactors at the Finsen Institute emphasized: "In propor- tion to their sale creams, lotions and powders containing neomycin were rare- ly connected with sensitization. This investigation suggests that neomycin ointments are the major cause of sensitization to this antibiotic." How thorough is the neomycin overkill? Four years after publication of Raab's and Hjorth's reports a regulatory agency proposed to deny further certification of selected neomycin consumer products based on a literature review that did not include the work of either. Example IV A few years ago a dermatologist was shocked by the remark that the diag- nosis of hair-dye dermatitis in his patient due to an allergy to p-phenylene- diamine (PPD) was circumstantial at best and could scientifically be false furthermore, his admonition that the patient never dye her hair again may be needlessly condemning her for life to a hair color she finds most obnox- i,ous. The ease he presented was straightforward enough: a woman of 38 years was unhappy with her prematurely greying brown-black hair. It made her look and feel 10 years older. She was convinced it was creating domestic problems. For 2 years, .on a regular 8-10 week schedule, she had dyed her hair to its normal uniform color with great success and personal satisfaction. Twenty-four hours prior to each application a carefully executed skin patch test as described by the manufaeturer had been performed and found to be negative. However, the morning after the last hair coloring procedure, which was carried .out in every detail as to technic and product, exactly as those which preceded it, the patient awoke with redness, itching, roughness, and swelling about the ears and hair line with accentuation over forehead and upper eyelids. When the patient presented herself and her story to the same dermatolo- gist several hours later, the eruption had grown more severe. A tentative diagnosis ,of hair-dye dermatitis was made immediate treatment with topieal and oral eortieosteroids was instituted. Recovery was prompt and complete. A month later, as scheduled, the patient returned for a diagnostic 48-hour

SKIN PATCH TEST 157 closed skin patch test with fresh 2% PPD in pctrolatum, the recognized stan- dard concentration and vehicle. Upon removal of the patch a one to two- plus reaction was observed twenty-four hours later the test site was clearly confirmed as a strong one-plus reaction. A contralateral control site with pet- rolatum alone was negative In the intervening month between treatment and test, information was received from the manufacturer that the hair color- ing product in question was of the "permanent" or oxidation type and con- tained PPD and related dye intermediates in its formulation. Despite the clinical and laboratory evidence in this patient, the final diag- nosis of allergic eczematous contact type dermatitis due to PPD could be and was wrong. The admonition against further exposure to hair coloring prod- ucts was unnecessary. A. A. Fisher and this author have studied a number of PPD patch test-positive individuals who tolerate repeated and routine ex- posure to PPD-containing hair coloring products without adverse reactions. (7,8). Such individuals demonstrate a one-plus or slightly greater reaction to the 4S-hour closed skin patch test with 2% PPD in petrolatum. The manufac- turer's recommended open 24-hour skin test with the product is usually nega- tive in such subjects. This open type product-use-skin test is more practical as a screening procedure than previously realized. Any number of common household products, allergens as well as primary irritants-from hair spray to oven cleaner-used the evening before the ap- pearance of the eruption could have accounted for the patient's presenting dermatitis. The presence of an allergic state proven by skin patch test does not neces- sarily reflect a subject's threshold of response tmder actual conditions of ex- posure to the consumer product. Dose relationship under contrived test con- ditions are not the same as dose relationships under use conditions. SUMMARY The foregoing are a few examples of many. They are offered as representa- tive of the ongoing confusion to which the scientific, medical, and industrial communities should direct their attention. The skin patch test is a valuable means to an end. Rigid discipline is required to avoid reversal of this equa- tion. A beguilingly simple procedure provokes an extremely complex biologic mechanism subject to all the vagaries that can be associated with the re- spome of living tissue. It behooves the practitioner to be humble in his in- terpretation. Perhaps the cause-and-effect relationship seemingly confirmed by skin patch test data may be mere coincidence. Does it stand the test .of time? Is the relationship reproducible by others? A local .or a temporary situation or the zeal of an investigator are worthy of consideration. Established scientific pnb- lications might act more critically toward disseminating valuable contribu- tions. Newsletters would be a better means for expressing personal experi-