Food-additive-induced urticaria: A survey of 838 patients with recurrent chronic idiopathic urticaria

Background: Recurrent chronic idiopathic urticaria (RCIU) is a common skin condition that affects 0.1-3% of the population in the USA and Europe and accounts for nearly 75% of all 'ordinary' chronic urticaria (CU) cases. Methods: We studied 838 consecutive patients with RCIU referred to hospital between 1998 and 2003. Patients with known causes of CU were excluded. Clinical history, physical examination, and symptom diaries were evaluated during two periods, a diet-free period (1 week) and a food-additive-free diet (FAFD) period (4 weeks), respectively, and two double-blind placebo-controlled (DBPC) challenges of six food additives were administered. The first DBPC challenge included a mixture of the six food additives (DBPC _mixed) given to all patients. The second DBPC challenge comprised the single food additives, administered at increasing doses (DBPC _single) to patients with a positive DBPC _mixed test and 105 patients with a negative DBPC _mixed test, as a control. Results: The DBPC _mixed challenge was positive in 116 patients. None of the 105 control patients had a positive DBPC _single test. Only 31 DBPC _single tests were positive in patients with positive DBPC _mixed challenge. Twenty-four of the 116 patients showing a positive DBPC _mixed challenge also had a positive DBPC _single result. Conclusions: Our results confirmed that food additive hypersensitivity reactions occurred in few RCIU patients using DBPC _single challenge. The combination of the results of FAFD and DBPC _mixed challenge seems to be of considerable practical interest for allergists, internists and dermatologists, rather than the data of clinical history and the results of DBPC _single challenge, in patients with RCIU.