Carmine allergy in urticaria patients

Introduction
Carmine, a commonly used natural red dye, can cause immediate and delayed allergic reactions, which are frequently overlooked.

Aim
To assess the incidence of carmine allergy and its clinical significance based on the placebo-controlled oral challenge in urticaria patients and suspected hypersensitivity to food additives.

Material and methods
Patients’ histories were recorded by means of a standardized questionnaire. The subjects underwent skin prick tests and patch tests for carmine, while the level of specific IgE was measured in 52 patients. The patients with at least one positive carmine test or with suspected hypersensitivity to carmine were suggested to undergo a placebo-controlled oral challenge test.

Results
One hundred and ten patients were enrolled in the study. Carmine skin testing was positive in 22 patients: skin prick tests were positive in 17% (n = 19), while patch tests were doubtful in 6% (n = 6). In 25/52 patients, the level of specific IgE was min. 0.01 kU/l. Oral challenge was performed in 33 subjects. Allergy to carmine was diagnosed in nine patients (8%); all of them suffered from chronic inducible urticaria.

Conclusions
Carmine is a potential allergen in patients with chronic inducible urticaria especially with concomitant systemic symptoms. Skin tests and specific IgE level measurement may be helpful tools to diagnose E120 hypersensitivity.