COSMETIC ALLERGY By N•ELS HJORTH, M.D.* Presented September 17, 1958, International Symposium, Copenhagen, Denmark NEARLY ALL PRODUCTS are capable of provoking allergic reactions in some of the consumers. Cosmetic allergic reactions are due to a sensi- tization to one or several of the ingredients. The major symptoms are itching, later redness and inflammation of the skin. Certain chemical substances have empirically been shown to be partic- ularly liable to give rise to allergic sensitizations. The sensitizing prop- erties of new, synthesized substances can seldom be predicted. However, in case of close chemical relationship to other substances with known high sensitizing potential, frequent sensitizations must be expected. This applies, for instance, to dyes related to para-phenylendiamine or to substances containing a para-aminophenyl radical. Likewise, cases of allergic reactions must be expected if the new substance is chemically related to sensitizers in common use by the consumers. Thus, house- wives who traditionally employ turpentine for household duties are liable to reactions from perfumes containing limonene or other terpenes. Apart from the chemical properties of a particular substance, the con- centration in which it is employed is all important for the incidence of sensitizations. Further, the vehicle may be of some consequence, partly by promoting the absorption of the substance, and partly because the surfactants used as emulsifiers in creams may induce a proliferation of the epidermal cells which has been shown to render the skin more susceptible to sensitization. The incidence of cosmetic allergy cannot be accurately estimated be- cause only a minority of the cases are seen by the dermatologists or are otherwise brought to the attention of the manufacturers. Among the 25,- 000 cases examined during the last twenty years at the greatest out- patient department here, only 550 cases could be ascribed to some cosmetic product as verified by a positive eczematous patch test. * The Finsen Institute, Copenhagen, Denmark. 96

COSMETIC ALLERGY 97 Among the 550 cases, 157 were due to allergy to creams, 67 to lipsticks and 57 to face powders. Compared to foreign clinics we have seen very few cases of eczematous reactions to nail lacquer (13 cases) and strikingly few to hair dyes (19 cases). This may possibly be due to a relatively low consumption of the products in this country. Allergy to perfumes is rare. Less than 1 per cent of all patients with eczema showed allergy to perfumes in toilet soaps. Creams, alcoholic lotions and brilliantine for the hair accounted for fifty cases of eczema, shampoos only for six cases. It is of some interest to note that the inci- dence of allergy to emulsifying fats was rather high, namely Lanette wax (32 cases), lanolin (21 cases) and cetylan (17 cases). Considering the wide variety of products and the intimate and prolonged contact with the skin, the incidence of cosmetic allergy in this selected group of the population is remarkably low. For comparison it must be mentioned that allergy to nickel is demonstrated in between 3 and 4 per cent of all the patients seen, while allergy to all cosmetic products only occurs in about 2 per cent.