By Gary M. White, MD
Multiple bed bug bites on the hand.
The bite of Cimex lectularius causes very itchy urticarial lesions. This bug comes out at night and bites the exposed skin (often of the hands, arms, and face) of the patient while s/he sleeps. See also insect bites and flea bites.
Bed bugs (Cimex lectularius) have been reported to cause four types of skin eruptions: 1) papular lesions with central punctum, 2) small grouped vesicles (produced by a single bite), 3) giant urticarial wheals up to 20 cm in diameter, and 4) unilateral hemorrhagic nodular or bullous lesions of the hands and feet. In addition, anaphylaxis has occurred. The distribution of lesions depends upon the type of clothing worn to bed. The face and arms are favored sites as they are more often exposed and readily accessible at night. Bed bugs are nocturnal and are most active just before dawn. They hide in cracks and crevices--avoiding light. They respond to heat and carbon dioxide and thus are attracted to sleeping individuals. They feed on the individual's blood and inject saliva which contains an anticoagulant.
The clinical history and exam (red, very itchy bumps, recent onset, occurring on arms, neck, and face) are often highly suggestive. A biopsy may be done to confirm the patient is being bitten but will not say which insect is doing the biting. Sleeping in a different room or even a different domicile/hotel may be necessary to confirm the bedroom as the source of the rash.
The source of exposure should be eliminated. An exterminator with specific experience in bed bugs may need to be called. Chemical control may be combined with environmental management, e.g., wash bed linens daily with hot water, vacuum clean rooms and bed linens, and steam clean furniture [An Bras Dermatol. 2015 Mar-Apr; 90(2): 240–243].
In an interesting study, bed bugs that fed on humans three hours after the human consumed ivermectin 200 ug/kg were much more likely to die than controls (63% 20-day mortality rate vs. 8% in the control group.) [J Emerg Med. 2013 Sep;45(3):433-40].
Don't keep clothes or bags on the floor. Study the bed and the area within three feet of the bed. Bed bugs are most likely to be hiding near the headboard. They also like right angles so examine bed frames, mattress piping, drawers, and windows. Look for round brown splotches/stains (from bed bug droppings) on the mattress and other fabrics.
This bed bug was actually crawling on the patient's shirt. The patient asked, "Do you think this could be causing my itchy spots?"
Two bedbug bites on the knee.
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