Summary The role played by dietary chemical factors in the pathogenesis of chronic idiopathic urticaria (CIU) was assessed in seventy‐six patients by challenge. Stable remission was first established by using an empirically established ‘exclusion diet’. A diet modified to exclude those chemicals giving a positive response to challenge was demonstrated to be of therapeutic value for time periods of up to 18 months. Re‐testing twelve patients at 12 months indicated that most patients positive to salicylate or benzoate challenge retained this pattern of reactivity.

Exclusion diets may have a practical place in determining of precipitating dietary factors in certain clinical conditions. We present an exclusion diet which is based on the exclusion of food commonly known to cause food allergies, and the exclusion of food which contains salicylates, benzoates, tartrazine, yeast, and penicillin. This provided a basis for challenge with these additives and natural chemicals. Preliminarv information in urticaria suggests a use for this diet h some allergic conditions.