Chronic allergic-like dermatopathies in nickel-sensitive patients. Results of dietary restrictions and challenge with nickel salts.

Nickel frequently contaminates foods. In sensitized patients, dietary nickel can cause a relapse of contact eczema and also widespread chronic dermatopathies quite similar to those triggered by authentic food allergy (IgE-mediated), from atopic dermatitis to chronic urticaria with angioedema. The present study was intended to evaluate the the results of an elimination diet and of the oral challenge test with nickel salts in a population of adults suffering from chronic urticaria or angioedema, pruritus or atopic dermatitis, and concomitant contract sensitization to nickel salts. The study involved a population of adult patients (112 subjects, 106 women and 6 men, aged from 16 to 58, mean age 29 +/- 10) with widespread allergic-like dermatopathies and contact sensitization to nickel salts (positive patch test). All of these subjects were prescribed a low nickel diet for four weeks. The patients who recovered or whose clinical manifestations greatly improved underwent an oral double-blind, placebo-controlled challenge: they were administered two successive, noncumulative doses of 10 and 20 mg nickel sulphate hexahydrate, respectively equal to 2.23 and 4.47 mg of elemental nickel. A search for specific IgE and the check on skin reactivity by skin-prick test against nickel were carried out in the patients who had shown particularly severe reactions after the oral challenge. A low nickel diet was effective in controlling the symptoms in 44 patients (39.28%, among whom there was one man). The oral double-blind, placebo-controlled challenge test was positive in all the patients who had favourably responded to the elimination diet, except one. In the patients with anaphylactoid reactions on the oral challenge, skin-prick tests were negative and no serum-specific IgE antibodies against nickel were found. Such findings appear to demonstrate that, in some patients with concomitant contact allergy, intolerance to ingested nickel salts might be the real cause of the onset and perpetuation of widespread, chronic, allergic-type dermatopathies.