Pseudoallergen-free diet in the treatment of chronic urticaria. A prospective study

In chronic urticaria, the possible pathogenetic role of pseudoallergic reactions to food has been repeatedly discussed, but stringent prospective studies regarding their clinical significance are not available. All patients with chronic urticaria and/or angioedema hospitalized at the department of dermatology during a period of 2 years were therefore included in a prospective study. Patients (n = 64) were screened for common causes of urticaria and then evaluated for possible benefits of a stringently controlled pseudoallergen-free diet. Double-blind, placebo-controlled oral provocation tests with food additives were performed on those patients benefitting from diet. In 73% of patients, symptoms ceased or were greatly reduced within 2 weeks on diet, although only 19% of them responded to individual pseudoallergens on provocation tests. Of the remaining patients, 11% responded to treatment of an associated inflammatory disease, and in 16%, no cause of the urticaria was ascertained. Follow-up at 6 months after hospitalization showed complete remission on diet in 46% and lasting improvement in all but one of the remaining patients on diet. An additive-free, stringently controlled diet thus provides a simple means of diagnosing and treating the majority of patients with chronic urticaria.