ABSTRACT
We conducted a prospective study at King Chulalongkorn Memorial Hospital, from June 2001 to November 2003, to identify the contribution of food allergy to urticaria in children. During the study period, 100 children with urticaria were enrolled, 36 of whom had a history suspicious of food allergy. Fifteen of 100 patients had fever (9 from upper respiratory tract infections, 4 from diarrhea and 2 from skin infections). A skin prick test (SPT) was positive in 15 of the 36 children who were suspected of having food allergy; 5 patients out of the positive SPT group had anaphylaxis due to food (2 from cow milk, 2 from wheat and 1 from egg). Six patients in the positive SPT group had a negative food challenge test (4 from open challenges and 2 from double-blind placebo-controlled food challenges [DBPCFC]). The other 4 patients of the positive SPT group refused the food challenge test. The parents of a patient who had urticaria from egg refused the skin prick test; an oral challenge test confirmed the diagnosis of egg allergy. One of the 21 patients that had a negative SPT had shrimp allergy proven by DBPCFC. Of the 64 patients who had no history related to food, SPT was done in 27 patients and revealed a positive result in 7 patients, all of whom had a negative food challenge test (4 with open challenge and 3 with DBPCFC). Urticaria from food was found in 7% and was suspected in another 4% of the patients. Severe reactions to food like anaphylaxis may occur. SPT alone is not adequate in making the diagnosis of food allergy; it must be confirmed by a food challenge test. Thirty percent of patients that did not have a history related to food had false positive SPT. Without a history suspicious of food allergy, SPT yields only minimal benefit.