Are You Confident of the Diagnosis?

Bed bugs (Cimex lectularius) are an increasingly common problem in the United States and throughout the world. Their resurgence has been linked to increased domestic and international travel, a lack of societal awareness, a change in pesticide use patterns, and increasing bed bug resistance to common pesticides. These insects are red-brown in color and typically grow to a size of 4 or 5mm in length, slightly longer than wide (Figure 1 and Figure 2).

Figure 1.

Cimex lectularius, the bed bug. Courtesy CDC/Piotr Naskreki.(Image is in the public domain.)

Figure 2.

An adult bed bug. Its flattened shape helps it to hide within tiny crevices. (Courtesy of Whitney Cranshaw,

Continue Reading

Their bodies are flattened (about the width of a credit card), helping them fit within tiny hiding places and avoid easy detection. They spend the day hidden within tiny crevices, such as cracks in a floor or wall, or within the seams of a mattress (Figure 3).

Figure 3.

Multiple bed bugs hiding within a mattress seam(Courtesy of Gary Alpert,

  • Characteristic findings on physical examination

During the early morning hours, when humans are typically in their deepest sleep, bed bugs emerge and feed on their victim. Due to an anesthetic within the bed bug saliva, the bites are typically painless and most victims never feel the bites as they occur. Bed bug bites cause typical arthropod bite reactions: a small pink papulovesicle that is highly pruritic in sensitive individuals (Figure 4). Some bite reactions may be delayed by up to a week or more after the initial bite Figure 5).

Figure 4.

Classic pattern of linear arthropod bites seen in bed bug bites (Courtesy of Howard Pride, MD).

Figure 5.

Bullous and crusted lesions due to bed bug bites (Courtesy of Renee Straub, MD and Andrea Zaenglein, MD).

Bed bug bites tend to occur in uncovered areas such as the arms or legs because the bed bug has difficulty biting through most types of clothes. Conversely, one study found that the face is one of the least likely areas to suffer bite reactions.

Bed bugs typically live together in large numbers; as a result, multiple bites often occur simultaneously. The “breakfast, lunch and dinner” sign refers to the tendency of multiple bites to take on a linear array. However, in practice this sign is neither sensitive nor specific for bed bug bites.

Diagnosis requires identification of C. lectularius in combination with typical cutaneous findings. Other clues to the presence of bed bugs include a sweet, musty or syrupy odor to the infested area (when large numbers of bugs are present) or red-brown blood stains on sheets from bed bug fecal material.

There are myriad ways of detecting the presence of bed bugs. Thorough visual inspection of typical hiding places during the day can be productive. Bed bugs spend the day in undisturbed, dark places, typically within 10 to 20 feet of the host. Power outlets, vents, cracks or holes in the wall or floor, loose molding, peeling wallpaper, mattress seams, even defects within the bedposts serve as suitable hiding places.

In the office setting, upholstered chairs, couches, areas where clothing are hung, under desks, bundled wires, and any place where workers congregate are useful areas to search. Sticky traps can be used in suspect areas, although they are not 100% sensitive in detecting the presence of bed bugs.

Dogs can be trained to sniff out bed bugs and bed bug eggs. This technique can be very sensitive, especially when visual inspection fails. Dogs are also used to confirm successful eradication efforts.

  • Expected results of diagnostic studies

Biopsy and serologic testing are of limited value in the diagnosis of bed bug bites. Pathology shows a typical bite reaction: there is often epidermal spongiosis, dermal edema, and a wedge-shaped dense lymphohistiocytic inflammatory infiltrate with numerous eosinophils. These findings are not specific for bed bug reactions and can be seen in any arthropod bite reaction (Figure 6 and Figure 7).

Figure 6.

Bed bug bite showing epidermal necrosis, papillary dermal edema and a superficial and deep perivascular mixed inflammatory infiltrate with numerous eosinophils.

Figure 7.

Closeup of Figure 6 showing perivascular lymphoid infiltrate, endothelial swelling and numerous eosinophils.

  • Diagnosis confirmation

The differential diagnosis includes other arthropod bites, including scabies infestation. As mentioned earlier, most arthropod bites look similar both clinically and histologically. Other differentials to include are drug or medication allergies, folliculitis, id reactions, dermatitis herpetiformis, viral exanthems, herpetic infections, and contact or irritant allergic dermatitis.

Bullous lesions in children may mimic chicken pox, bullous impetigo, or immunobullous disease such as bullous pemphigoid or chronic bullous disease of childhood. Immunobullous disease such as bullous pemphigoid should also be considered in elderly patients. Biopsy, culture, and a complete history typically can differentiate these entities.

Who is at Risk for Developing this Disease?

Bed bugs are attracted to humans by body warmth and by carbon dioxide. They show no sex, racial, or economic discrimination when choosing their victim. Studies have shown that approximately 75% to 96% of adults have a cutaneous reaction to bed bug bites, and the rate of sensitivity increases (and the response time decreases) with the increasing exposure. However, surveys of people living in infested buildings suggest that elderly patients do not react as commonly as younger adults or children. In that same survey, those who reported more vigorous reactions to mosquito bites were more likely to report suffering bite reactions from bed bugs as well. This may reflect an individual’s propensity to develop an allergic reaction to antigenic stimuli, rather than true cross reaction.

Persons who travel frequently and those who sleep in places where others have recently slept are at an increased risk of being exposed. Travelers may unwittingly acquire bed bugs within their belongings, where bed bugs can hitch a ride to infest the household. Any place where people congregate or spend significant amounts of time are at risk of becoming infested. This includes apartments, group homes, shelters, hotels, nursing homes, hospitals, clinic waiting rooms, dormitories, cruise ships, trains, cinemas, and brothels. If humans are unavailable, C. lectularius can feed on pets until a more suitable host becomes available. Bed bugs can live for up to a year without feeding, but an individual bug will typically feed every 5 to 20 days.

What is the Cause of the Disease?

  • Etiology

  • Pathophysiology

C. lectularius possesses skin-piercing mouthparts that it uses to suck the blood of its victim. The bed bug saliva contains an anesthetic as well as anticoagulants so that the bite is typically unnoticed by the victim, and blood flows freely from the bite site. It is believed that cutaneous reactions to bed bug bites result from IgE-mediated hypersensitivity to components of bed bug saliva, including nitrophorin, factor X, and an apyrase-like nucleotide-binding enzyme. IgE specific to nitrophorin has been demonstrated in patients who react to bed bug bites.

Systemic Implications and Complications

Despite a number of investigative studies, bed bugs have not been shown to be important vectors of any infectious or systemic illness. An exceptional case of anemia in an elderly patient was reported due to massive numbers of bed bug bites. Excoriations may lead to impetiginization or rarely cellulitis. Rare cases of anaphylaxis have been reported.

Itching from bed bug bites can cause trouble sleeping, anxiety, and stress. In one survey, 29% of respondents reported insomnia or sleeplessness due to bed bugs. Victims may also suffer embarrassment, anger, frustration, and depression. These aspects of treatment should not be ignored or minimized by the treating medical professional.

A discussion of bed bug complications would be incomplete without mention of the financial impact a bed bug infestation may have. Apart from direct medical costs, bed bug eradication is expensive and often takes several treatments over a period of months. Sleeplessness, stress, and anxiety may cause decreased work productivity. Businesses such as hotels, clinics, and retailers may be forced to close their doors until eradication efforts are complete. Lost business from social stigmatization may result, even after reopening.

Because bed bugs may travel along electrical conduits or through cracks in walls, entire apartment buildings and similar residencies may need to be treated if a single unit is found to be infested, magnifying the costs of eradication and increasing the chances of inadequate treatment. Moreover, many bed bugs are becoming increasingly resistant to pesticides, forcing more frequent use of more expensive or potentially more dangerous chemicals.

Treatment Options

Goddard and deShazo recently reviewed medical therapy for bed bug reaction and found that oral antihistamines, topical steroids, and oral and parenteral steroids all had inconsistent efficacy in the published literature. I suggest the therapeutic ladder in Table I.

Table I.
Topical antipruritics and anesthetics
Topical steroids
Oral antihistamines
Intralesional steroids
Systemic steroids

For mild reactions, start with over-the-counter topical antipruritic and anesthetic agents such as camphor 0.5% or pramoxine 1% used several times a day. Strong topical steroids such as triamcinolone 0.1% or fluocinonide 0.05% can be used once or twice a day. Oral antihistamines, including cetirizine or loratadine 10 mg a day can also be helpful. Sedating antihistamines such as diphenhydramine or hydroxyzine are used at doses beginning at 10 to 25 mg at night. Systemic corticosteroids such as prednisone 0.5 to 1.0 mg/kg/d or intramuscular triamcinolone or prednisolone at 1 mg/kg can be efficacious in severe reactions.

Optimal Therapeutic Approach for this Disease

The best treatment for bed bugs is prevention. If you plan to travel, consider checking online to see if your scheduled lodgings have been infested ( Use hard plastic or metal luggage that snaps shut; bed bugs can squeeze through most zippered luggage and will be harder to find and eradicate in fabric-coated luggage. Keeping your clothing in bed-bug-proof plastic containers (such as BugZip) can prevent unwanted hitchhikers from following you home.

Upon arrival, inspect your hotel room for signs of bed bugs and have a back-up plan in case your scheduled lodgings are infested. Luggage racks should be used to minimize contact between your belongings and the surrounding room. When you return home, immediately launder all travel clothing and vacuum (or steam) your luggage to reduce the chances of introducing bed bugs to your home. Finally, if bed bugs are discovered, consider reporting your findings to an online registry, such as the one listed above.

If you live in an infested building, Vaseline on bed posts or placing bed posts in a shallow disk of mineral oil may help to prevent bed bugs from infesting your bed. This technique only works if the bedding and mattresses are free of infestation and the bed (including the sheets, pillows, or wires) is not touching anything but the floor.

Secondhand furniture should be thoroughly inspected before bringing it into the home. Similarly, if you have infested furniture, do not simply set it out on the curb lest someone else take it with them and infest their home. If you cannot treat the furniture, consider marking it with a sign to notify the unwary.

Ultimately, successful treatment of bed bugs requires elimination of the bed bug infestation. The Centers for Disease Control and Prevention (CDC) recommends a technique called integrated pest management, involving active participation by all affected individuals and culminating with the judicious use of chemical pesticides. Identification of bed bug hiding places, removing excess clutter, using physical modalities such as steamers and high-powered vacuums with a crevice tool, and sealing cracks and crevices are first-line treatments that all affected individuals can participate in.

Bed bugs are notoriously difficult to eradicate, considered by many to be more difficult than termites or roaches to get rid of. A fully licensed, experienced exterminator should always be contacted when bed bug infestation is confirmed or suspected. The CDC recommends that only licensed professionals apply chemical pesticides. Personal pesticide use cannot be condoned: pesticides, including illegal and potentially unsafe chemicals, are readily available and marketed towards bed bug infestations. Furthermore, it is well known that foggers or “bug bombs” are not effective against bed bugs.

Patient Management

Bed bugs show no sex or racial preference. Victims of bed bugs may feel that they are unclean. They should be reassured that bed bugs do not discriminate based on cleanliness or social status. High-end hotels, apartment buildings, home residencies, restaurants, offices, and clothiers are being increasingly affected by bed bug infestations.

Follow-up inspection with a reputable exterminator is necessary to ensure adequate treatment. Eradication of bed bugs from large residential complexes may be difficult and require many months of intensive treatment. Large commercial and industrial buildings also provide endless areas for bed bugs to colonize. In the workplace setting, high-traffic areas are prone to recolonization from employees with uncontrolled infestations at home, and all employees should be offered home inspections and treatment if this is a concern.

Unusual Clinical Scenarios to Consider in Patient Management

Because bed bug bites are delayed, pinpointing the time (and location) of exposure can be challenging. A traveling patient may think bed bug exposure occurred at home, rather than a hotel they stayed in the previous weekend. In addition, even when victims leave the site of exposure, new bites may continue to appear, causing patients to doubt the source of their condition.

What is the Evidence?

Reinhardt, K, Kempke, D, Naylor, RA, Siva-Jothy, MT. “Sensitivity to bites by the bedbug, Cimex lectularius”. Med Vet Entomol. vol. 23. 2009. pp. 163-6. (This is the first study to measure the rate of sensitivity to bed bugs, proving that not all victims of bed bug bites react.)

Potter, MF, Haynes, KF, Connelly, K, Deutsch, M, Hardebeck, E, Partin, D. “The sensitivity spectrum: human reactions to bed bug bites”. Pest Control Technology Feb. 2010. pp. 70-4,100. (Fascinating survey study showing that elderly patients may be less likely to respond to bed bug bites. In addition, sleeplessness, stress, and anxiety were not uncommon in bed bug bite victims.)

Pinto, L, Cooper, R, Kraft, S. “Bed bugs in office buildings: the ultimate challenge?”. Pest Control Technology. Feb 2010. pp. 2-9. (Provides guidance for investigating and dealing with suspected bed bug infestations in the office setting.)

“Joint Statement on Bed Bug Control in the United States from the US Centers for Disease Control and Prevention (CDC) and the US Environmental Protection Agency (EPA).”. November 22, 2010. (Excellent online review of bed bug manifestations and treatment.)

Doggett, SL, Russell, R. “Bed bugs- -What the GP needs to know”. Aust Fam Physician. vol. 38. 2009. pp. 880-4. (Excellent review covering most of the recent literature on bed bug pathophysiology, symptoms, prevalence, and differential diagnosis.)

” Bed bug information.”. December 8, 2010. (A free, valuable resource on bed bug biology, prevention, and treatment.)

(A comprehensive, informative free Web site run by a private consumer. The site is funded by paid advertising, but there is a lot of useful information that most readers can easily access.)

(Another comprehensive, informative, and free Web site run by a nonprofit organization, the National Pest Management Association. There is a lot of basic bed bug information, news releases, and an area to post questions that are answered by an NPMA associate.)

Foulke, GT, Anderson, BE. “Bed bugs”. Semin Cutan Med Surg. vol. 33. 2014 Sep. pp. 119-22. (A concise and excellent review.)

Delaunay, P, Blanc, V, Del Giudice, P, Levy-Bencheton, A. “Bedbugs and infectious diseases”. Clin Infect Dis. vol. 52. 2011 Jan 15. pp. 200-10. (Bedbugs are suspected of transmitting infectious agents, but no report has yet demonstrated that they are infectious disease vectors. The authors describe 45 candidate pathogens potentially transmitted by bedbugs.)

Quach, KA, Zaenglein, AL. “The eyelid sign: a clue to bed bug bites”. Pediatr Dermatol. vol. 31. 2014 May-Jun. pp. 353-5. (Authors observation of a physical exam finding associated with bedbugs.)