Update on idiopathic anaphylaxis.

Idiopathic anaphylaxis (AI) refers to anaphylaxis without a recognizable cause after a comprehensive allergic workup. The diagnostic approach usually includes an accurate clinical history aimed at excluding both the most and the less frequent causes of anaphylaxis and all pathologies that may resemble anaphylaxis. AI is more common in adults than in children. The epidemiology of AI has been reduced in recent years, probably to increase knowledge and discover new clinical entities, such as the α-gal anaphylaxis. Anaphylaxis results from the massive activation of the mast cells (MCs). Thus, it is also necessary to exclude MC disorders, such as mastocytosis and mast cell activation syndrome, and α-tryptasemia, which may manifest with IA symptoms.