Hypersensitivity of azo dyes in urticaria patients based on a single-blind, placebo-controlled oral challenge

Abstract

Introduction: The role of azo dyes in urticaria is not fully understood.

Aim: To assess the incidence rate of hypersensitivity reactions to food azo dyes based on a placebo-controlled oral challenge in a group of patients with suspected urticaria exacerbation after consuming food additives.

Material and methods: The study included patients over 18 years of age with chronic urticaria, in whom hypersensitivity to food additives was suspected based on a questionnaire and medical history. Patients suspected of urticaria exacerbations after ingestion of azo dyes were enrolled in a placebo-controlled single-blind oral challenge (OC) with a mixture of azo food dyes: tartrazine, Quinoline Yellow, Sunset Yellow, Cochineal Red, Allura Red, and azorubine.

Results: Out of 110 patients (76 women and 34 men, mean age 46.1 (20-76 years), 39 patients were qualified for the oral challenge. We observed two subjects (5.1%) with a positive result.

Conclusions: Azo dyes ingested in food or medications incidentally cause urticaria but may exacerbate its course. Oral challenge-confirmed hypersensitivity to azo dyes is much less common than reported by patients.

Keywords: Cochineal Red; Quinoline Yellow; Sunset Yellow; food additives; tartrazine; urticaria.