Food additive-induced chronic pruritus: further evidence

Abstract

Conflict of interest: none declared. The role of food additives in pseudoallergic disorders has been debated for years, and an impressive number of clinical conditions have been ascribed to these substances in the past. It is now generally accepted that most older studies of food additive intolerance were poorly controlled and have led to unproven results.1 If only those studies that were carried out using rigorous methods are considered, the number of conditions that can definitely be associated with food additive intolerance drops dramatically. One of these few clinical conditions is chronic generalized pruritus. Two recent case reports described patients with generalized pruritus induced by sodium nitrate.2, 3 The present study adds one further case of chronic pruritus caused by two distinct food additives. A 56‐year‐old man presented with a 6‐month history of severe pruritus on the trunk, upper limbs and head with no visible skin rash. During the previous months he had been prescribed cetirizine 10 mg daily with little benefit. He reported no personal or familiar history of atopic diseases. Skin‐prick testing with a large panel of commercial food extracts (Abello 1 : 20 wt/vol) and with airborne allergens was negative. Autologous serum skin test4 did not elicit any skin reaction. After exclusion of diseases associated with itching without apparent skin eruption (hyperthyroidism, lymphomas, parasitoses, polycythaemia vera and hepatic diseases5) by appropriate laboratory and radiographic investigations, an elimination diet (free of food additives) was started. From the fifth day of the diet, the patient noted a marked reduction in pruritus, and it totally disappeared within 10 days. After 1 month of the additive‐free diet, during which the patient remained totally symptom‐free, an open challenge (consisting of an unrestricted diet for 15 days) was performed. After 1 week, the pruritus re‐appeared with the same distribution as previously. The additive‐free diet was resumed and, again, symptoms totally disappeared after 5–6 days. After 3 weeks without symptoms, the patient underwent double‐blind, placebo‐controlled oral challenges with food additives. He gave informed written consent before challenges were started, and continued the elimination diet throughout the entire challenge period.