largely on the person's (abnormal) allergy response. Here's what I just Googled:
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Fire ant venom differs from bee and wasp venom, which are mostly proteinaceous solutions. About 95% of fire ant venom is water-insoluble and nonproteinaceous and contains dialkylpiperidine hemolytic factors. These hemolytic factors induce the release of histamine and other vasoactive amines from mast cells, resulting in a sterile pustule at the sting site. These alkaloids are not immunogenic, but their toxicity to the skin is believed to cause the pustules to form.
The venom also contains several allergenic proteins, measuring about 1.5% by dry weight. Four major allergenic proteins exist; Soli 1-4 induce immunoglobulin E (IgE) responses, including anaphylaxis, in patients who are allergic. Antigenic similarity exists between these proteins and bee and wasp venoms.
Many patients have venom-specific IgE-mediated wheal and flare reactions that develop over hours into pruritic edema, induration, and erythema that persist for up to 72 hours. These reactions may involve an entire extremity. These lesions histologically resemble late-phase mast cell–dependent reactions and show an infiltrate of eosinophils, neutrophils, and fibrin deposition. Large, local reactions rarely can cause edematous tissue compression, leading to vascular compromise of an extremity.
Frequency:
* In the US: Because most fire ant stings are not severe enough to cause the person being stung to seek medical attention, estimating the frequency of stings is difficult; however, annually, more than one half of the population in endemic areas is stung, and the number is increasing.
Mortality/Morbidity: Fire ants are becoming an increasingly important public health concern in the United States. More than 80 fatalities have been reported from fire ant-induced anaphylaxis.
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http://www.emedicine.com/derm/topic607.htm"More than 80 fatalities have been reported from fire ant-induced anaphylaxis."
pnorman