^* 50% fatal anaphylaxis in UK is iatrogenic. Beta-lactam antibiotics are the commonest cause of medication-induced anaphylaxis. Drugs may cause mast cell degranulation through both IgE-mediated (allergic) mechanisms or direct mast cell activation. The latter reactions, sometimes termed anaphylactoid, are clinically indistinguishable from IgE-mediated reactions but may occur without previous exposure, that is, first dose reactions.

^† Peanuts and tree nuts (e.g. Brazil nuts, cashew nuts and walnuts) are the commonest causes of food anaphylaxis, and along with wheat, egg, fish, seafood, soya and milk are responsible for over 90% of reactions. Cofactors are increasingly recognized as being important in food anaphylaxis: in their absence a foodstuff will be tolerated but in their presence a reaction will occur. Recognized cofactors include exercise, NSAIDs and alcohol. Food-dependent exercise-induced anaphylaxis (FDEIA) requires the presence of the trigger food and exercise and may occur even if exercise is taken up to 4h after the foodstuff is ingested.

^‡ Responsible insect varies worldwide – bee and wasp in UK.