DermDx: Itchy Rash on Shoulders, Trunk


  • Slide

A 34-year-old man is referred for evaluation of a rash affecting his shoulders and trunk. He states that the condition is extremely itchy and has been worsening over the past few weeks. He has a history of alcoholism and substance abuse and currently resides at a halfway house. He is unaware of other residents with a similar rash; at least 2 residents own cats. Examination reveals multiple erythematous papules in the affected areas.

The term bedbug refers to the obligate parasitic arthropod Cimex lectularius, the common bedbug, and less commonly its tropical cousin C hemipterus.1 Bedbugs have coexisted with humans for centuries and can be traced to Egyptian tombs dating over 3000 years.2...

Submit your diagnosis to see full explanation.

The term bedbug refers to the obligate parasitic arthropod Cimex lectularius, the common bedbug, and less commonly its tropical cousin C hemipterus.1 Bedbugs have coexisted with humans for centuries and can be traced to Egyptian tombs dating over 3000 years.2 In the mid-20th century, approximately 30% of US households were infested with bedbugs; however, the incidence markedly decreased with the introduction of pesticides during World War II.3 In the last decade, a significant resurgence of bedbugs has occurred that is attributed to a combination of factors such as an increase in international travel, pesticide resistance, and inadequate pest control programs.4,5

Bedbugs are oval, reddish-brown, flat, and wingless insects ranging in size from 4 to 7 mm in length.6 The usual life cycle of bedbugs is approximately 6 months with some bedbugs living 12 months or longer.6 These photophobic parasites do not live on their human hosts but rather hide in the seams of mattresses, crevices of bed frames, walls, and furniture during the day and bite their human hosts at night, typically just before dawn.5,6 Bedbugs are attracted to heat and carbon dioxide emitted from the human body.7 Their saliva contains several anesthetic, vasodilatory, anticoagulant, and proteolytic compounds that contribute to hypersensitivity reactions.8-10

Diagnosis of bedbug bites is based on clinical history and appearance. Typical lesions are pruritic, erythematous papules with a central hemorrhagic crust or vesicle.11 The classic bedbug rash is referred to as “breakfast, lunch, and dinner” because it commonly presents as several bites in a row or cluster.12 Bites may vary in number with a preferential distribution more common on unclothed areas such as the face, neck, and extremities.6

Skin eruptions typically resolve within 1 to 2 weeks without treatment. Systemic reactions such as asthma, generalized urticaria, angioedema, and very rarely anaphylaxis have been reported.13 There is no evidence that any treatment regimen alters the natural history of bedbug dermatitis. If pruritis is present, nonprescription topical antipruritic preparations and topical corticosteroids can be of benefit. Management is often costly and disruptive to everyday life engendering significant psychological distress.14 In most infestations, consultation with a professional exterminator is advised.

Alexandra Stroia, BS, is a medical student at the Lake Erie College of Osteopathic Medicine in Erie, Pennsylvania; Stephen Schleicher, MD, is director of the DermDox Dermatology Centers, associate professor of medicine at Geisinger Commonwealth Medical College, and clinical instructor of dermatology at Arcadia University and Kings College.


  1. Ibrahim O, Syed UM, Tomecki KJ. Bedbugs: helping your patient through an infestationCleve Clin J Med. 2017;84(3):207-211. doi:10.3949/ccjm.84a.15024
  2. Usinger RL. Monograph of Cimicidae (Hemiptera–Heteroptera), Vol 7. Entomological Society of America; 1966;7:50.
  3. Paul J, Bates J. Is infestation with the common bedbug increasing? BMJ. 2000;320(7242):1141.
  4. Romero A, Potter MF, Potter DA, Haynes KF. Insecticide resistance in the bed bug: a factor in the pest’s sudden resurgence? J Med Entomol. 2007;44:175-178.
  5. Studdiford JS, Conniff KM, Trayes KP, Tully AS. Bedbug infestation. Am Fam Physician. 2012;86(7):653-658.
  6. Delaunay P, Blanc V, Del Giudice P, et al. Bedbugs and infectious diseasesClin Infect Dis. 2011;52(2):200-210. doi:10.1093/cid/ciq102
  7. Sfeir M, Munoz-Price LS. Scabies and bedbugs in hospital outbreaksCurr Infect Dis Rep. 2014;16(8):412. doi:10.1007/s11908-014-0412-2
  8. Valenzuela JG, Ribeiro JM. Purification and cloning of the salivary nitrophorin from the hemipteran Cimex lectulariusJ Exp Biol. 1998;201(pt 18):2659-2664. doi:10.1242/jeb.201.18.2659
  9. Valenzuela JG, Guimaraes JA, Ribeiro JM. A novel inhibitor of factor X activation from the salivary glands of the bed bug Cimex lectulariusExp Parasitol. 1996;83(2):184-190. doi:10.1006/expr.1996.0065
  10. Valenzuela JG, Charlab R, Galperin MY, Ribeiro JM. Purification, cloning, and expression of an apyrase from the bed bug Cimex lectularius. A new type of nucleotide-binding enzymeJ Biol Chem. 1998;273(46):30583-30590. doi:10.1074/jbc.273.46.30583
  11. Goddard J, deShazo R. Bed bugs (Cimex lectularius) and clinical consequences of their bitesJAMA. 2009;301(13):1358-1366. doi:10.1001/jama.2009.405
  12. Cohen PR, Tschen JA, Robinson FW, Gray JM. Recurrent episodes of painful and pruritic red skin lesionsAm J Clin Dermatol. 2010;11(1):73-78. doi:10.2165/11311140-000000000-00000
  13. Bircher AJ. Systemic immediate allergic reactions to arthropod stings and bitesDermatology. 2005;210(2):119-127. doi:10.1159/000082567
  14. Doggett SL, Russell R. Bedbugs—what the GP needs to knowAust Fam Physician. 2009;38(11):880-884.
Next hm-slideshow in Derm DX