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Almost anything can be a potential allergen (Box 21.3). Common agents include medications, foods and food additives, latex, arthropod bites and stings, mold, radiographic contrast media, and certain marine envenomations [1] (see Chapter 38). Some insect bites or stings, such as those of millipedes, caterpillars, and centipedes, most often cause only pain and local skin reactions such as blistering [4, 5]. Certain species of caterpillars have venom‐filled hair and spines that can cause systemic reactions, including anaphylaxis, within 2 hours of the sting [4]. Bites from kissing bugs are painless and usually occur during sleep. Most often, this results in localized swelling at the bite site, but can progress to systemic reactions [6]. There are also occasional rare reports of anaphylaxis from the bites of horse flies, deer flies, rats, and mice.

Hymenoptera account for the majority of severe allergic responses and anaphylaxis related to insect bites. There are three families of Hymenoptera: bees (honey bees and bumble bees), vespids (yellow jackets, hornets, and wasps), and stinging ants (fire ants). Since fire ants are in the Hymenoptera order, the venom in fire ant bites is similar to that of bees and hornets, thus a patient allergic to bee stings will also display an allergic reaction to a fire ant bite [7]. Africanized honeybees (“killer bees”) are an aggressive hybrid of the honeybee and have the same venom and sting repeatedly, thus increasing the risk of a severe reaction [8]. Approximately 1% of children and 3% of adults have reportedly had severe systemic allergic reactions to Hymenoptera venom [9]. Anaphylaxis can occur with a first‐time exposure. Insect stings are the only allergen for which specific immunotherapy currently exists. This is most likely due to the prevalence and severity of such responses in humans [10].