Summation anaphylaxis: A challenging diagnosis.

Anaphylaxis is the most severe of allergic reactions. The most frequent triggers of anaphylaxis in childhood are food, insect venom, drugs, exercise, etc. In some cases, the presence of more than one trigger is necessary for the allergic reaction, while one trigger alone is tolerated. This rare condition is called summation anaphylaxis (SA). Food-dependent exercise-induced anaphylaxis is the most well-known SA. However, SA may also occur with the association between food and/or exercise plus one or more of the following other cofactors, such as drugs, especially non-steroidal anti-inflammatory (NSAID), alcohol, infections, temperature variation, and menstrual cycle. SA can explain some cases of idiopathic anaphylaxis, as well as cases of an apparent breakdown in a previously acquired tolerance for food, or finally, when faced with a suggestive clinical history of food allergy or exercise anaphylaxis and the provocation test is negative. In these situations, a more careful clinical history looking for other cofactors is necessary.