Background: In adult patients with chronic urticaria (CU), the prevalence of food allergy is low compared to childhood patients. However, there are many patients who report food-related aggravation of CU, and some of them may have histamine intolerance. Objective: The aim of this study was to evaluate the role of ingested histamine and to investigate the effect of a histamine-free diet in adult patients with CU.

Methods: Twenty-two adult patients with CU were enrolled. Foods with high amounts of histamine were prohibited to all patients for four weeks. The degree of severity of the urticaria was evaluated using the urticaria severity score (USS) and urticaria activity score (UAS). Plasma histamine levels and diamine oxidase (DAO) activity were determined and compared before (baseline) and after the histamine-free diet.

Results: Twenty-two adult patients were recruited and completed four weeks of histamine-free diet. The USS and UAS scores each showed significant differences before and afte the histamine-free diet ( =0.010, =0.006).