Allergic reactions to insect stings range in pattern and severity from relatively harmless to fatal. A detailed history and appropriate diagnostic tests can identify those who need the protection of venom immunotherapy to prevent life-threatening reactions to future stings. Providing the best guidance to patients requires a knowledge of the patterns of reaction, the natural history of the disease, and the utility and interpretation of diagnostic tests. Insect bites cause toxic rather than anaphylactic reactions and are discussed further in Chapter 190.
Systemic reactions (including anaphylaxis) to insect stings occur in 3% of adults and 0.5% to 1% of children. Fatal reactions are rare and may occur on the first reaction, but most of these deaths can be avoided with appropriate treatment, including venom immunotherapy. The frequency of allergic reactions to insect stings is related to the frequency of exposure, occurring more often in beekeepers and in rural areas.
The different families of Hymenoptera have different behaviors and degrees of aggressiveness. Honeybees (Apis mellifera) are minimally aggressive and will sting only in defense, such as being accidentally grabbed or stepped on. Africanized honeybees (Apis mellifera scutellata), which are indistinguishable from ordinary honeybees and do not have more potent venom, are much more aggressive and often sting in swarms. In contrast, yellow jackets and hornets (Vespula, Dolichovespula, and Vespa species) are more aggressive and will sting with less provocation. The paper wasps (Polistes) are less aggressive than are the vespids but tend to build their nests near buildings and under eaves, rendering them more likely to encounter people and contribute to a large number of stings. Imported fire ants (Solenopsis) are present throughout the Gulf coast and southeastern United States, and as many as 50% of people living in infested areas get stung each year. This danger is particularly true for children when they play outside.
Hymenoptera stings normally cause swelling, redness, and pain at the site of the sting, with a rapid onset within minutes and resolution within hours. This reaction is expected and does not require medical treatment but may be relieved with ice, antihistamines, and analgesics. Unusual nonallergic reactions to stings include serum sickness-like reactions, neurologic reactions (peripheral and central neuropathy, seizure), or toxic reactions (constitutional). They can be caused by a single sting, but toxic reactions usually are related to a large number of stings. Anyone who has sustained more than 50 stings should be monitored for the complications of Hymenoptera venom overdose, which includes rhabdomyolysis, renal failure, and myocardial infarction.
Large local reactions occur in 5% to 10% of people who are stung. They represent immunoglobulin (Ig) E-mediated reactions and cause prolonged swelling contiguous with the sting site, with delayed onset 6 to 12 hours after the sting, increasing for 24 to 48 hours, and ...