Written and peer-reviewed by physicians—but use at your own risk. Read our disclaimer.

banner image

amboss

Trusted medical answers—in seconds.

Get access to 1,000+ medical articles with instant search
and clinical tools.

Try free for 5 days

Scabies

Last updated: March 24, 2021

Summarytoggle arrow icon

Scabies is a parasitic skin infestation caused by the Sarcoptes scabiei var. hominis (S. scabiei) mite, which is primarily transmitted via direct human-to-human contact. The female scabies mite burrows into the superficial skin layer, causing severe pruritus, particularly at night. Primary lesions commonly include erythematous papules, vesicles, or burrows. Treatment involves topical medical therapy (e.g., permethrin) and decontamination of all clothing and textiles.

  • Pathogen: Sarcoptes scabiei var. hominis
  • Transmission
    • Highly contagious
    • Typically via direct physical (skin-to-skin or sexual) contact
    • Rarely indirect transmission (e.g., sharing textiles such as bedding, towels, or clothes)
    • Commonly affects children and individuals living closely with other people (e.g., in nursing homes or jails)
  • Risk factors: crowded living conditions (e.g., institutions such as nursing homes, child care facilities, and prisons) [1]

References:[2][3]

  • The fertilized, female mite tunnels into the superficial skin layer (stratum corneum), forming burrows in which she lays her eggs and deposits feces (scybala).
  • After 2 months, the female parasite dies on site.
  • Following a period of 3 weeks, the larvae mature into adult mites, maintaining the infestation cycle.
  • The excretions of the mites and their decomposing bodies contain antigens which cause an immunological response (see type IV hypersensitivity reaction), presenting as severe pruritus and excoriations.

References:[4]

  • Incubation period: approximately 3–6 weeks following infestation.
  • Intense pruritus that increases at night [5]
  • Burning sensation
  • Skin lesions
    • Elongated, erythematous papules
    • Burrows of 2–10 mm in length
    • Scattered vesicles filled with clear or cloudy fluid
    • Excoriations, pustules, and secondary infection
    • Bullous or nodular formation (especially in children)
    • Formation of crusts
    • Post-inflammatory hyperpigmentation
  • Predilection sites
    • Wrists (flexor surface)
    • Medial aspect of fingers
    • Interdigital folds (hands and feet)
    • Male genitalia (e.g., scrotum, penis)
    • All other intertriginous areas of the skin (anterior axillary fold, buttocks)
    • Areas surrounding the nipple (mamillary region)
    • Periumbilical area or waist
    • Knees (flexor surface)
    • Elbows
    • Feet (dorsal and lateral aspect)
    • Additionally in children, elderly persons, and immunosuppressed patients: scalp, face, neck, under the nail, palms of hands, and soles of feet

References:[6]

Scabies may be mistaken for eczema, especially as the topical use of glucocorticoids initially alleviates symptoms.

Bed bugs

  • Pathogen: Cimex lectularius
  • Transmission: direct contact with infested furniture, mattresses, bed frames
  • Risk factors: crowded, unsanitary living conditions
  • Clinical features
    • Asymptomatic red punctum at the site of the bed-bug bite
    • Localized skin reactions on exposed skin
      • Painless, erythematous papules
      • Size: 2–5 mm
      • Often appear in a linear pattern
      • Pruritus is common
      • Resolve spontaneously within 1–2 weeks
  • Diagnostics
    • Consult a pest control service
    • Detection of bed bugs in the patient's environment confirms the diagnosis
  • Treatment

The differential diagnoses listed here are not exhaustive.

  • Medical therapy: topical application of a scabicidal agent
    • Drug of choice: permethrin 5% lotion
    • Alternatives
      • Lindane 1% lotion: in the case of treatment failure or side effects
        • Mechanism of action: blocks GABA channels → neurotoxicity in the mite
      • Oral ivermectin: especially indicated in large outbreaks or severe forms of scabies
      • Others: crotamiton 10% cream or lotion, sulfur ointment
    • Symptomatic treatment of pruritus
    • All close contacts should receive prophylactic treatment.
  • General measures
    • Wash all textiles (e.g., clothing and bedding) (day 1 and day 8 post-treatment)
    • All contacts within the household should be treated for scabies infestation even if asymptomatic.

We list the most important complications. The selection is not exhaustive.

  1. Parasites - Scabies - Epidemiology & Risk Factors. https://www.cdc.gov/parasites/scabies/epi.html. Updated: November 2, 2010. Accessed: May 4, 2017.
  2. Management of Scabies. http://www.ifd.org/protocols/scabies. Updated: January 1, 2017. Accessed: May 4, 2017.
  3. Walton SF, Currie BJ. Problems in Diagnosing Scabies, a Global Disease in Human and Animal Populations. Clin Microbiol Rev. 2007; 20 (2): p.268-279. doi: 10.1128/CMR.00042-06 . | Open in Read by QxMD
  4. Bugs, Bites, and Stings. http://www.clevelandclinicmeded.com/medicalpubs/diseasemanagement/dermatology/bugs-bites-and-stings/. Updated: April 1, 2012. Accessed: May 4, 2017.
  5. Euroform Healthcare » Skin Diseases - Sauer Notes. http://www.euroformhealthcare.biz/skin-diseases/sauer-notes-uvo.html. Updated: October 6, 2016. Accessed: May 5, 2017.
  6. Parasites - Scabies - Disease. https://www.cdc.gov/parasites/scabies/disease.html. Updated: November 2, 2010. Accessed: May 5, 2017.
  7. Parasites - Scabies - Control. https://www.cdc.gov/parasites/scabies/health_professionals/control.html. Updated: November 2, 2010. Accessed: May 5, 2017.