What causes ant stings?

Updated: Nov 08, 2018
  • Author: Randy Park, MD; Chief Editor: Joe Alcock, MD, MS  more...
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Ants account for one half of all insects. While many ant species sting, the most aggressive in the United States are imported fire ants, Solenopsis invicta. These ants fiercely guard their territory and attack intruders in large numbers, inflicting thousands of stings and bites to victims unable to escape. Fire ant venom is 95% alkaloid, which is unique among ants. A fire ant typically bites with its mandibles, then swivels its abdomen and stings repeatedly in an arc about the bite site. Their stings develop into sterile pustules and then rupture, leaving crusted wounds that may become infected secondarily. Patients have survived as many as 5000 fire ant stings. Brazilian fire ants, S invicta, have nearly eradicated native ant species in their range from Florida to Texas and north to Arkansas and South Carolina. S invicta is found in South and North America in areas where mean high temperatures are 15°C or higher.

Stings from other ants often closely resemble those of wasps and bees, although with less tissue destruction and less severity. Harvester ants, Pogonomyrmex species, inject venom containing a hemolysin. This sting frequently creates an ecchymotic area surrounding the sting site. Some species of field ants truly bite with the mandible and spray the acidic toxin into the wound without injecting venom. Formic acid, a component of ant venom uncommon in bee or wasp stings, is derived from the superfamily name Formicidae. Ant stings cause generalized reactions less often than stings from flying Hymenoptera.

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