72
Bites and Stings
Insects
• The bite of any insect can lead to a local cutaneous reaction whose intensity can vary depending on the individual’s level of sensitivity; the typical presentation is a 2 to 8 mm, erythematous urticarial papule in an exposed area (Fig. 72.1); lesions are often multiple and can be grouped.
Fig. 72.1 Insect bite reactions. In this patient, there are papulovesicles as well as excoriated papules with hemorrhagic crusting. In more darkly pigmented individuals, residual hyperpigmentation is common and can persist for months. Courtesy, Julie V. Schaffer, MD.
• Secondary changes consisting of excoriations may be present; less often, vesicles or bullae develop at the site of bites (Fig. 72.2).
Fig. 72.2 Insect bite reactions. Sometimes patients develop large, erythematous, edematous plaques (A) or frank bullae (B). Courtesy, Julie V. Schaffer, MD.
• Bite reactions typically resolve over 5–10 days; occasionally, patients develop persistent bite reactions that on biopsy may be diagnosed as pseudolymphoma (see Chapter 99).
• Postinflammatory hyperpigmentation is common, especially in patients with darkly pigmented skin.
• Secondary infection is a potential complication, most commonly from staphylococci or streptococci.
• Exaggerated bite reactions can be seen in patients with chronic lymphocytic leukemia; rarely, hypersensitivity reactions to mosquito bites that become necrotic can be associated with EBV infection (see Chapter 67).
• Anaphylaxis with urticaria and angioedema is generally due to stings from hymenopterids (bees, wasps, hornets, and fire ants) (Fig. 72.3).
Fig. 72.3 Fire ant bites presenting as clusters of sterile pustules on the foot. Courtesy, Dirk M. Elston, MD.
• Insects may be vectors of infectious diseases (Table 72.1).
Table 72.1
Major insects of dermatologic significance.
* See Chapter 71 for information on Tunga penetrans, a burrowing flea.
Photographs courtesy, Dirk M. Elston, MD.
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