Food-specific IgG4 lack diagnostic value in adult patients with chronic urticaria and other suspected allergy skin symptoms.

ABSTRACT

BACKGROUND: Specific IgG4 dosing against food is proposed to the public by a lot of commercial laboratories as a reliable method to diagnose food intolerance. Actually, few data on IgG4 responses to foods in adults are available in the literature. In this study we evaluated the clinical utility of specific IgG4 dosing against food in adult patients with suspected food allergy/intolerance. METHODS: A case series of 73 adult patients with suspected food allergy and clinical manifestations of chronic urticaria or other allergy-supposed skin symptoms were tested for specific IgG4 against foods. An open food challenge was carried out for all IgG4-positive food. All positive open tests were controlled by double-blind placebo-controlled food challenge. RESULTS: Forty-five patients (62%) were IgG4 positive for a number of foods, mainly egg, milk, casein and wheat. None of the patients with IgG4-positive testing showed adverse reactions, neither immediate nor delayed, to the corresponding food. CONCLUSIONS: In adult patients, testing for specific IgG4 lacks clinical utility for the diagnosis of food allergy or intolerance. Dosing of IgG4 should not be part of the diagnosis and therapy of adult patients with allergy-like skin diseases.