What are the unique characteristics of fire ants and their sting?

The fire ant, accidentally introduced into the United States in the 1930s from Brazil, now occupies most of the Southeast, limited only by cold winter weather in the north and the deserts of the Southwest. When the ants are provoked, they may attack en masse, administering up to several thousand stings to a victim. The sting is actually initiated by the ant biting the flesh and then pivoting slightly and repeatedly stinging the victim to form an annular eruption of sterile pustules and sting reaction sites. The sting site develops a large wheal and flare punctuated by a small sterile pustule, which ulcerates and potentially scars. The large erythematous wheal will then gradually desquamate over the next couple of days, and the sting site resolves normally. The unusual fire ant venom, a piperidine alkaloid, has become a leading cause of anaphylactic reaction to venomous animals in the United States. Treatment of the ant stings is symptomatic. Select patients with severe local or generalized sting reactions may be considered for immunotherapy.

Nguyen SA, Napoli DC: Natural history of large local and generalized cutaneous reactions to imported fire ant stings in children, Ann Allergy Asthma Immunol 94:387–390, 2005.