Allergy to stings by insects of the order Hymenoptera, which incudes bees and wasps, are a cause of considerable morbidity. Adverse reactions to Hymenoptera stings are classified into normal local reactions, large local reactions, systemic toxic reactions, systemic anaphylactic reactions, and unusual reactions. In most people, stings by bees and wasps cause normal local reactions that resolve without treatment. However, up to 26% of individuals may experience large local reactions and up to 4% may experience systemic reactions, which are potentially fatal. This paper gives an overview of the epidemiology, clinical manifestations, diagnosis, treatment, and outcome of bee and wasp sting allergy, along with a discussion of some aspects of Hymenoptera venom immunotherapy, the only effective treatment of insect sting-induced anaphylaxis. Suggestions also are given regarding how to avoid stings.