Anaphylaxis: current state of knowledge for the modern physician.

Anaphylaxis is a severe, potentially fatal, hypersensitivity reaction of rapid onset. It may trigger life-threatening cardiopulmonary compromise, often with skin and mucosal changes such as urticaria and angioedema. The prevalence of anaphylaxis is increasing and the number of cases of fatal anaphylaxis appears to be rising. Food, insect stings, and drugs are the most common triggers. Novel triggers are increasingly seen and include delayed anaphylaxis to red meat, food-dependent exercise-induced reactions and anaphylaxis to monoclonal antibodies. Anaphylaxis is usually IgE mediated, but other mechanisms also play a role for example direct mast cells activation. Differential diagnosis is discussed including asthma, syncope and shock; excessive endogenous histamine, food related syndromes, and some rare diagnoses. Intramuscular epinephrine is first line treatment. The role of other drugs is reviewed. Timed and serial serum tryptase measurements help to confirm the diagnosis. Long-term management is necessary to minimise the risk of recurrence and includes identification of the trigger(s), management of risk factors, education on avoidance and a formalised treatment plan with an epinephrine auto-injector if appropriate. Every patient who has experienced anaphylaxis should be referred to an allergy clinic for appropriate management. This is endorsed by many national guidelines (eg, UK NICE). Anaphylaxis is often misdiagnosed or miscoded as, for example, asthma or food allergy. Most doctors will encounter a patient with anaphylaxis in their career and should to be familiar with the clinical features, management and mechanisms of this potentially fatal condition.