[Dietetic interventions in allergic contact dermatitis--when are they reasonable?].

This paper focuses on three questions of dietetic interventions in allergic contact dermatitis: 1) in which cases it is justified to suspect that an ingested hapten causes allergic reaction, 2) how to verify the causal relationship between the hapten and current disease, and 3) in which cases dietary interventions are justified? Clinical studies, cases, and reasoning collated in this article indicate that contact allergy to food haptens should be suspected when symptoms are consistent with the clinical picture of systemic reactivation of allergic contact dermatitis or systemic photoallergy. Positive patch test result is not sufficient as confirmation of causality--the clinical relevance should be judged by means of double-blind placebo-controlled provocation with hapten in question. If such challenge appears not feasible, the relevance may be confirmed indirectly by the clearance of symptoms after introducing a low-hapten diet with remission lasting for at least 4 weeks after withdrawal of pharmacotherapy, and the recurrence of symptoms following the return to the old diet. In the majority of cases, "nickel-free" or "low nickel" diets are burdensome and with no real benefit. Nickel is the fifth most abundant element on Earth and even most restrictive diets could reduce nickel load by 50% at best. In the EU alone, 65 million people are allergic to nickel, while only 1-11% of patients with clinical nickel allergy will experience benefits from "nickel-free" diets. Indiscriminate introduction of such dietary regimens based merely on positive patch test results poses a considerable burden to individuals and society, therefore, it is not recommended.