Contact dermatitis in patients with leg ulcers.

The incidence of contact allergy to 63 substances, including active principles and excipients used in a variety of topical preparations, has been studied by patch testing in 306 patients being treated conservatively for stasis dermatitis with or without ulceration. Positive reactions to one or more test compounds were recorded in 177 patients. The main offenders among drugs were neomycin, sulphonamide and promethazine; among the excipients, they were parabens, lanolins and benzoyl peroxide. Frequent reactions were observed to certain substances of the 'para' group, benzocaine, diaminodiphenylmethane, aniline and paraphenylendiamine, with the first three acting mainly as indicators of cross-sensitization. The extension and spread of allergic dermatitis can also be produced by drugs administered systematically. Recognition of the allergens responsible for allergic contact dermatitis arising at the lower leg site is a necessary condition if chronicity and spread of the dermatitis are to be prevented. For the same reason it is important to restrict topical applications to non-allergic substances.