Merck Manual

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James G. H. Dinulos

, MD, Geisel School of Medicine at Dartmouth

Reviewed/Revised Dec 2021 | Modified Sep 2022
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Bedbug bites are usually painless but cause reactions, often pruritic, in susceptible patients. Diagnosis is clinical. Treament is symptomatic treatment of bites and chemical and physical eradication of bedbugs.

Etiology of Bedbugs

Bedbug infestations have become more common in the developed world in recent years. The most common bedbugs affecting humans are Cimex lectularis (in temperate climates) and C. hemipterus (mainly in tropical climates). Bedbugs hide in cracks and crevices of mattresses, other structures (eg, bed frames, cushions, and walls; in areas with less than optimal living conditions such as mud houses and thatched roofs). They multiply exponentially; a few bedbugs multiply to thousands within 2 to 3 months. They move slowly and are attracted to people by warmth and carbon dioxide. Bedbugs bite exposed skin, usually at night. A feeding is completed in 5 to 10 minutes. Bedbugs are not known to transmit infections to humans.

Symptoms and Signs of Bedbugs

Lesions are generally on exposed skin. They develop some time between the morning after and 10 days after being bitten. Lesions can be any of the following:

  • Puncta only

  • Purpuric macules

  • Erythematous macules, papules, or wheals, often pruritic, each with a central hemorrhagic punctum

  • Bullae

Lesions may form linear patterns or may be seen in groups. Older adults develop symptoms less often than do younger people. Lesions resolve after about 1 week. Secondary infection can develop.

Patients may be anxious about the difficulty and expense of eradicating a bedbug infestation and about the social stigma that can result from infestation. They may isolate themselves to avoid spreading infestation.

Diagnosis of Bedbugs

  • Clinical evaluation

Diagnosis based on lesion appearance may be difficult because the appearance is usually nonspecific. However, most bedbug bites are larger and more edematous than other bites (eg, flea bites).

Identification of bedbugs can help confirm the diagnosis. Bedbugs have flat, oval, reddish brown bodies. After a blood meal, the body is less flat and more reddish. Adult C. lectularis are about 5 to 7 mm in length, and C. hemipterus are slightly longer. Bedbug feces or blood may be evident on bed linens or behind wallpaper.

Treatment of Bedbugs

  • Symptomatic treatment

Bedbug bites are treated symptomatically (eg, with topical corticosteroids and/or systemic antihistamines) as needed.

Bedbugs should be eradicated using physical and chemical means. Physical means include vacuuming affected areas and laundering suspect articles, then drying them on the dryer's hottest setting. In addition, entire rooms should be treated professionally, when possible, by heating to temperatures ≥ 50° C (122° F) or with multiple insecticides. Bedbugs and eggs on infested items are killed when frozen at -20° C (-4° F) for at least 2 hours; however, placement in most home kitchen freezers is typically insufficient (1 Anticoagulants and their sites of action Anticoagulants and their sites of action ).

Treatment reference

  • 1. Parola P, Izri A: Bedbugs. N Engl J Med 382(23):2230–2237, 2020. doi: 10.1056/NEJMcp1905840

Key Points

  • Consider bedbug bites particularly if initially asymptomatic lesions cluster linearly on exposed skin.

  • Search for evidence of infestation to help confirm the diagnosis.

  • Recommend professional assistance to help eradicate bedbugs.

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