Allergy to food additives
While there are many reports in the literature suggesting adverse effects, intolerance, or allergy to food additives, not many studies have used skin-prick or scratch tests with food additives. Researchers from the University of Turku in Finland report on the use of this standard technique, in combination with oral provocation tests, as a method of determining which patients with urticaria and angioedema might benefit from an additive-free diet. The study group consisted of 91 subjects suffering from chronic or recurrent urticaria or recurrent angioedema with a duration of two months or more, and a control group of 247. Skin-prick and scratch tests were performed on all subjects and controls with preservatives (sodium benzoate, benzoic acid, sodium glutamate, p-aminobenzoic acid, parabens, propionic acid, sorbic acid, citric acid, sodium metabisulfite) and nine food colors. Subjects and controls were selectively given oral provocation tests, in some cases with increasing doses. Skin tests showed at least one positive reaction in 24/91 subjects with urticaria or angioedema and 24/247 controls. Oral provocation tests on 10 of the skin-test positive patients showed only one positive reaction, to benzoic acid. All 91 subjects were advised to follow an additive-free diet, to be evaluated by a retrospective postal survey. Seventy subjects returned the questionnaire: among the 23 skin-test positive subjects responding, 18 had followed the diet, and 16 of them had experienced marked relief. Among skin-test negative subjects, 42/47 followed the diet and 17/42 reported significant improvement. Among the self-selected adherents to the additive-free diet, there was a favorable response both in the skin-test positive and negative subjects. Based on these results, the authors suggest that skin test results may have a predictive value in identifying patients who may respond to an additive-free diet.