What are the physical findings characteristic of bedbug bites?

Updated: Mar 26, 2020
  • Author: Robert A Schwartz, MD, MPH; Chief Editor: Dirk M Elston, MD  more...
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Most commonly, exposed skin is affected. Bedbug bites are painless, but pruritus and purpuric macules may appear. Their distribution depends on the bite site, whether it be the face, neck, hands, arms, lower legs, or generalized; however, they often are evident on the face upon awakening in the morning.

Papules, urticaria, or bullae may predominate together with signs of secondary infection. The bullae are rarely severe. [26] A hemorrhagic puncta may be evident. If a person is not sensitized, no symptoms may be evident, only a purpuric macule at the bite site. Targetoid and edematous plaques may be evident, mandating distinction from erythema multiforme and Sweet syndrome. [27]

Bites are often noted in linear groups of 3, sometimes called "breakfast, lunch, and dinner," evident as erythematous papules, sometimes with a prominent urticarial component in predisposed individuals.

Note the images below.

Bedbugs feeding on a human host. Courtesy of Colon Bedbugs feeding on a human host. Courtesy of Colonel Dirk M. Elston, MD (from Elston, 2000).
Bedbug bites themselves are typically painless. Ho Bedbug bites themselves are typically painless. However, the subsequent allergic reaction that may develop can cause intense pruritus. While feeding, bedbugs may inject one of several pharmacologically active substances, including hyaluronidase, proteases, and kinins. These compounds may induce different skin reactions, such as erythema, wheals, vesicles, or hemorrhagic nodules. Repeated bites may sensitize individuals, leading to more pronounced cutaneous manifestations or systemic hypersensitivity reactions. The local trauma from bedbug bites can lead to secondary bacterial infection, causing ecthyma, cellulitis, or lymphangitis. There is some evidence that bedbugs may also be a vector for hepatitis B and Chagas disease. Histologic findings from bite-site biopsy specimens typically show eosinophilic infiltrates, which are indicative of the allergic nature of the reaction. The image shown is papular urticaria, which may develop from bedbug bites.

Go to Papular Urticaria and Acute Urticaria for complete information on these topics.

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