Ninety-one subjects suffering from chronic or recurrent urticaria or recurrent angioedema of 2 months to 17 yr duration were skin-prick and scratch tested with 18 various food additives. Twenty-four of the subjects (26%) had at least one histamine equivalent skin test (ST) reaction. In contrast, only 24 (10%) of 247 non-urticaria control subjects showed comparable results. An oral provocation test with food additives was carried out on 10 of the 24 ST-positive subjects with urticaria or angioedema, but only one positive reaction, caused by benzoic acid, was recorded. All 91 subjects were advised to follow an additive-free diet. The effect of the diet was investigated with a retrospective postal survey. Twenty-three ST-positive subjects returned the questionnaire, 18 had followed the diet, and 16 (89%) of these 18 had experienced marked relief of their symptoms. Correspondingly, 42 of the 47 ST-negative subjects had followed the diet, and 17 (40%) had improved. The difference was significant (P < 0.05). Our results suggest that skin tests with food additives can be used to measure skin hyperreactivity and that they may have a predictive value in identifying patients who will respond to an additive-free diet.
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