eMedicine Specialties > Dermatology > Environmental

Bedbug Bites

Author: Robert A Schwartz, MD, MPH, Professor and Head, Dermatology, Professor of Pathology, Pediatrics, Medicine, and Preventive Medicine and Community Health, UMDNJ-New Jersey Medical School
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Updated: Jun 10, 2009

Introduction

Background

Arthropod assaults on humans can have many manifestations clinically, histologically, and immunologically. Hemiptera is an order of insect species. This order of "true bugs" has piercing-sucking mouthparts and includes the family Cimicidae (bedbugs), which are blood-sucking ectoparasites of mammals or birds. All Cimex species organisms are reddish brown insects. Cimex lectularius are 5-7 mm in size. Females are slightly larger than males. Cimex hemipterus organisms are approximately 25% longer than C lectularius organisms. Females deposit fertilized eggs in cracks or crevices, with newborns emerging in 4-5 days.

Pathophysiology

The mechanism of skin injury by arthropods depends on the structure of the mouthparts. These insects are categorized as vessel feeders if they insert the tip into a capillary or as pool feeders if they feed on the extravasated blood from damaged tissue. They often inject different pharmacologically active substances (eg, hyaluronidase, proteases, kinins), which may cause different skin reactions (eg, erythema, wheal, vesicle, hemorrhagic nodule). The type of reaction provoked depends on previous exposure; repeated bites may lead to an allergic reaction, which may lead to pronounced cutaneous manifestations. Some patients show a severe systemic hypersensitivity to arthropod allergens. The site of the bite can also become secondarily infected with bacteria infection and lead to ecthyma, cellulitis, and/or lymphangitis.

Susceptibility to arthropod bites depends on many external factors (eg, occupation, conditions of employment, cohabitation with a variety of domestic animals, housing, climate, clothing). An arthropod is usually attracted to its host by body heat, carbon dioxide in exhaled air, vibration, human sweat, and/or odor. The Cimex (bedbug) genus attacks both mammals and birds. C hemipterus (the tropical bedbug) bites mostly humans and is found in warm climates, whereas C lectularius (the common bedbug) also attacks bats and domestic animals (eg, chickens).

Bedbugs are 5-7 mm in length with reduced wings. The mouthparts are modified for piercing and sucking. They live between wooden floorboards, in furniture, in bed frames, in mattresses, or behind peeling paint. Bedbugs sneak out to grasp human skin with their forelegs, pierce the skin, and inject anticoagulant- and anesthetic-containing saliva. Bedbugs normally feed at night, usually approximately an hour before dawn. However, if the conditions are favorable, they also feed during the day. Feeding takes 3-12 minutes. In proper conditions, adult bedbugs can survive without a meal for a year or longer. Each female lays approximately 300 eggs in her lifetime. The eggs hatch in 10 days. The nymph stage lasts 6 weeks, undergoing 5 molts.

Insect bites, including those from the bedbug, have been proposed as a factor contributing to the formation of a cutaneous reaction termed papular urticaria. Patients with papular urticaria have been shown to demonstrate immunoglobulin G antibodies to bedbug (C lectularius) antigens.² Thus, immunoglobulin G against C lectularius, Cimex pipiens, and Pulex irritans in patients with papular urticaria may contribute the pathogenesis of this condition.

Frequency

United States

This infestation is relatively common.

International

This infestation is common and worldwide, a problem particularly in poor regions of the world.³ The rate of bedbugs (Cimex hemipterus) was 37.5% in children's beds from a rural region of The Gambia.
 
Bedbugs have allegedly been introduced from abroad into Seoul, Korea, because no reports on bedbugs have existed for more than 20 years.⁴

Mortality/Morbidity

Bedbug bites can create considerable anxiety and localized and occasionally systemic reactions. Sometimes, if the bite reactions are intensely pruritic, scratching with excoriations may be complicated by impetigo.

• Bedbugs may be a vector for hepatitis B⁵ and, in endemic areas, for American trypanosomiasis (Chagas disease).⁶ See Chagas Disease (American Trypanosomiasis) and Hepatitis B for more information on these diseases. Of note, reports have indicated the risk of insect transmission of HIV, if any, is extremely low and likely nonexistent.^7,8
• Anaphylactoid reactions are well described. One case of an anaphylactoid reaction occurred in a 41-year-old businessman in a first-class urban hotel in America.

Race

All people are affected. No racial or ethnic predisposition is known.

Sex

No sexual preference is known in bedbug attacks.

Age

No age predisposition is known.

Clinical

History

• The bites often occur at night because bedbugs are nocturnal, with peak activity just before dawn.
• Bedbugs are resourceful and opportunistic insects. In one well-documented daytime outbreak, its victims were all women who rode a particular English tram. Each woman had a peculiar band of erythema studded with bullae on the back of both calves.
• Repeated exposure to external bedbug bites leads to skin reactions. In one sample from 2009, 18 of 19 persons had a skin reaction after bedbug exposure, but usually only after repeated controlled exposure. With repeated exposure, the latency between the bite and the skin reaction decreased from about 10 days to a few seconds.⁹
• Visually searching beds for bedbugs may be useful. It may be more efficient to survey the corners of bed nets and mattresses.
• Bedbugs produce a peculiar pungent odor familiar to building inspectors and tenement dwellers.
• With a heavy infestation, specklike masses of dung may be evident behind wallpaper and at other sites. This dung contains blood elements.
• Confirming the diagnosis of a bedbug bite sometimes is difficult. Obtain a detailed history of the home environment, work conditions, and presence of domestic animals.
• As reported by Leibold et al¹⁰ in 2003, a disseminated bullous eruption with systemic reaction caused by C lectularius may occur, but is rare.

Physical

• Most commonly, exposed skin is affected.
• Bedbug bites are painless, but pruritus and purpuric macules may appear.
• Their distribution depends on the bite site (eg, face, neck, hands, arms, lower legs, generalized); however, they often are present on the face upon awakening in the morning.
• Papules, urticaria, or bullae may predominate together with signs of secondary infection. The bullae are only rarely severe.¹¹
• 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.
• 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.

Causes

• Bedbugs can be seen anywhere, but they tend to occur in environments in disarray. Old furniture makes an excellent home for bedbugs. They also like to hide in the seams and folds of mattresses and in bed frames and springs.

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