[Skin reactions to food and food constituents--allergic and pseudoallergic reactions].

Which skin reactions, with allergic or pseudo-allergic mechanism, are actuated by food? Contact urticaria or "forme-fruste-anaphylaxis" is the most common. Tests, using purchasable allergen extracts, mostly produce negative results, due to inadequate natural identity. Therefore, scratchtests with the natural antigens are necessary. Apart from the acute and chronic urticaria, classic other reaction types (Coombs and Gell) within the scope of real food allergy are also present (allergic vasculitis from meat containing penicillin, thrombocyopenic purpura after taking aspirin or quinine); cellular immune reactions to food and its components are also not uncommon. The importance of natural salicylate for the aetiopathogenesis of chronic urticaria has not yet been ascertained; nevertheless, a suitable diet is recommended on the understanding that degranulation of the mast cells, possibly due to subclinical stimuli, is triggered off.