Fast Five Quiz: Bites and Stings

Richard H. Sinert, DO


April 29, 2019

Oral antihistamines and topical corticosteroids are recommended in most patients with multiple fire ant bites; nevertheless, some practitioners still use prednisone or other systemic steroids to treat patients with numerous lesions. Systemic corticosteroid use is controversial in patients with extensive lesions who do not have systemic allergic reactions or generalized skin reactions. Large doses of corticosteroids and intravenous fluids may complicate the treatment of patients with preexisting cardiovascular disease. The immunosuppressive effect of corticosteroids may predispose patients to secondary infection.

Minor fire ant bite reactions have an excellent prognosis. Severe reactions have an excellent prognosis with early and appropriate treatment. However, fire ants are becoming an increasingly important public health concern, especially in the United States. More than 80 fatalities have been reported from fire ant-induced anaphylaxis.

Skin lesions produced by fire ants typically occur in clusters. The attachment site of the ant's mandibles makes two small, hemorrhagic puncta. The initial reaction to the sting is the development of a wheal, followed within 24 hours by a sterile vesicle. The fluid in the vesicle becomes cloudy; after 8-10 hours, the typical lesion is an umbilicated, sterile pustule on a red, edematous base. The pustule may last for several days and is characteristic for fire ant stings. The pustule then ruptures, forms a crust, and heals several days later, sometimes leaving small scars. Excoriation and open erosions may lead to secondary infection.

Laboratory studies are not necessary for most people with fire ant stings; however, in severe reactions, a CBC count, coagulation studies, and a urinalysis could be obtained for the following uncommon but possible manifestations:

  • Leukocytosis

  • Thrombocytopenia

  • Hypofibrinogenemia

  • Abnormal coagulation

  • Disseminated intravascular coagulation

  • Proteinuria

  • Hemoglobinemia

  • Hemoglobinuria

  • Myoglobinemia

  • Myoglobinuria

  • Azotemia

Read more on fire ant bites.

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