Anaphylaxis to insect venom.
Systemic reactions to insect stings have a prevalence of about 1% in the adult population. The majority presents with urticaria and angioedema, and the number of deaths per year registered as due to insect stings is 0.1-0.5 per million in the general population. The venom contains peptides and low molecular weight substances such as histamine with an effect on blood vessels, smooth muscles and nerves. High molecular weight components in the venom often have enzyme activity and in addition can act as allergens. It can be difficult to separate allergic from vasovagal or psychogenic reactions based on the clinical history alone. Skin test reaction to venom and/or venom specific IgE in the blood indicate an allergy although a high proportion of people in the general population (up to 20%) with no previous reactions are positive in such tests. Test results can be used to identify the responsible insect species, since allergic reactions can occur against species-specific as well as common allergens in the venom. Following a systemic allergic reaction only about half of the patients will react systemically to a future sting. Immunotherapy with insect venom is effective but the duration of the treatment is still under debate.