Idiopathic anaphylaxis.

Idiopathic anaphylaxis is not uncommon and can be found in as many as 60% of patients referred to an allergist for anaphylactic events. It is an extremely frustrating condition for patients because they have no means of avoiding a known allergen and events occur spontaneously and unprovoked. The objective of this study was to synthesize and review the medical literature on idiopathic anaphylaxis and present a strategy for diagnosis, prevention, and treatment of episodes. A literature review was performed after a search of PubMed using the key words of idiopathic anaphylaxis. Idiopathic anaphylaxis is more common in adults than in children and in women than in men. The symptoms and signs are identical to those found in other causes of anaphylaxis. Perhaps the most common entities to be considered in the differential diagnosis are somatoform reactions. The two most recent advances in our ability to detect the cause are the discovery that episodes can be caused by mast cell-activating syndromes, systemic mastocytosis, and IgE to galactose-alpha-1,3-galactose. Patients experiencing idiopathic anaphylactic episodes should, if possible, avoid taking drugs that may complicate therapy or worsen a reaction. Fortunately, the vast majority of cases follow a benign course. Although many recurrent episodes of anaphylaxis remain idiopathic, recent advances in our knowledge, especially the description of mast cell-activating disorders and the discovery of anaphylactic reactions to galactose-α-1,3-galactose have allowed us to find causes in events that previously would have been classified as idiopathic. In addition, the majority of such patients exhibit a diminishing frequency of reactions over time and can be managed in a way that prevents mortality and a severe effect on their quality of life.