History
A patient's reaction to a Hymenoptera sting determines the treatment required. Reactions may be graded as local, urticaria without systemic symptoms, and generalized. Emergency physicians should attempt to determine degree of reaction based on both patient history and a physical examination.
Rapid onset of symptoms is the rule; 50% of deaths occur within 30 minutes of the sting, and 75% occur within 4 hours.
Fatal allergic reactions can occur as the first generalized reaction. Far more common, however, is a fatal reaction following a previous, milder generalized reaction. The shorter the interval since the last sting, the more likely it is that a severe reaction will take place.
Large local reactions do not predispose patients to generalized reactions. Local reactions may be life threatening if local swelling at the sting site compromises the airway. Local reactions to stings can cause peripheral nerve block.
Local reactions may produce the following:
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Pain occurs immediately after sting.
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Edema is marked and may extend to 10 cm from site of envenomation.
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The insect frequently is seen by patient and may be identified from the description.
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Bleeding may occur at site of sting.
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Pruritus is common.
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Vasodilation may produce a sensation of warmth.
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The stinging apparatus may have been seen in the wound and removed prior to presentation.
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Nausea or vomiting may occur without generalization.
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If Hymenoptera are swallowed, stings can cause painful swelling in the mouth or esophagus.
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Visceral pain may occur with stings in the gastrointestinal (GI) tract after ingestion of the insect.
Urticaria may occur with or without the symptoms noted in local reaction.
Generalized reactions may produce the following symptoms:
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Urticaria
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Confluent red rash
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Shortness of breath, wheezing
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Edema in airway, tongue, or uvula
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Weakness, syncope
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Anxiety, confusion
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Chest pain
Physical Examination
Local reactions may include the following:
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Erythema, edema, warmth, tenderness
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Drainage from site of sting
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Compromised distal circulation as result of edema
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Distal sensation loss from stings over peripheral nerve
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Corneal ulceration from corneal stings
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With bee stings, stinging apparatus visible at sting site
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If Hymenoptera are swallowed, painful swelling in the mouth or esophagus
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Ant stings: Vesicles from fire ants, classic arc of fire ant stings, and ant stings on mucous membranes or conjunctival surfaces cause dramatic swelling in patients who are sensitive. See the image below.
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Fire ant bites. In less than 10 seconds, an unwary scientist was stung over 250 times on one leg when he carelessly knelt on a collapsed fire ant mound. The sterile pustules developed to this stage in 3 days. US Department of Agriculture. Courtesy of Wikimedia Commons.
Urticaria or generalized redness may develop without systemic symptoms.
Generalized reactions may include the following symptoms:
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Urticaria
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Vomiting
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Wheezing
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Tachypnea
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Hypotension
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Laryngoedema, lingular edema, uvular edema
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Delirium, shock
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Respiratory arrest
Complications
Sting sites may become infected. Infection is more common in fire ant stings because they frequently are multiple; stings vesiculate and then ulcerate, leaving pruritic open wounds.
Rebound anaphylaxis may occur in patients with generalized reactions as antihistamine and alpha-agonist levels subside after treatment.
Anaphylaxis may occur in susceptible patients from exposure to other insect-related material, including honey and apiotherapy.
Serum-sickness-type reactions may occur up to 14 days after a sting.
Myocardial infarction, [11] renal failure, DIC, rhabdomyolysis, [12] and cerebral edema may occur after a bee sting. [13] One case report documents transient inferior ST-segment elevation consistent with myocardial ischemia after a single wasp sting in a 58-year-old man. [14] In a retrospective analysis of medical records from 1985-2007, 7 of 45 pediatric patients were noted to have developed acute renal failure after a wasp sting. [15]
Peripheral nerve block may occur if sting is near the path of a nerve.
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Western paper wasp (Mischocyttarus flavitarsis) building a nest. By Sanjay Acharya (self-made at Sunnyvale, California, USA). Courtesy of Wikimedia Commons.
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Yellow jacket. By Richard Bartz, Munich aka Makro Freak (Own work). Courtesy of Wikimedia Commons.
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Fire ant bites. In less than 10 seconds, an unwary scientist was stung over 250 times on one leg when he carelessly knelt on a collapsed fire ant mound. The sterile pustules developed to this stage in 3 days. US Department of Agriculture. Courtesy of Wikimedia Commons.
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Fire ants. US Department of Agriculture. Courtesy of Wikimedia Commons.
