Scabies !
A very itchy skin infestation by a tiny mite that burrows into the skin, spreads by close contact and often affects whole families or institutions.
Updated 2026-11-01
Structures involved
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- Skin
- Proximal phalanx, middle finger
- Proximal phalanx, index finger
- Proximal phalanx, ring finger
- Wrist capsule
- Scrotum
Microorganisms that cause it
In the clinical exam
Why it happens
What it is
A contagious infestation of the epidermis by the mite Sarcoptes scabiei var. hominis, which causes intense itch, especially at night. Crusted (Norwegian) scabies is a severe form with huge numbers of mites in people with weak immunity.
Who gets it
The World Health Organization lists scabies as a neglected tropical disease; it affects many millions of people each year, most in hot, crowded and low-resource settings. In Latin America it is common in children, in crowded homes and in institutions such as care homes, prisons and shelters.
Causes
- The female mite burrows into the stratum corneum and lays eggs
- Spread by prolonged skin-to-skin contact (household, sexual partners, carers)
- Less often via shared clothing or bedding, much more so in crusted scabies
Risk factors
- Overcrowding and poverty
- Young children and older adults in care homes
- Immunosuppression (HIV, transplant, corticosteroids), malnutrition or neurological disease, which favour crusted scabies
- Sexual contact with an infested person
Pathophysiology
Mites, their eggs and faeces in the burrows provoke a delayed (type IV) hypersensitivity reaction. In a first infestation itch begins after 2–6 weeks, so people spread mites before they have symptoms; on re-infestation it starts within days. In crusted scabies a poor immune response lets thousands to millions of mites multiply in thick crusts.
Classification
- Classic scabies
- Crusted (Norwegian) scabies
- Nodular scabies
- Scabies in infants (palms, soles, face and scalp involved)
Symptoms and signs
- Intense itch, worse at night, often affecting several household members
- Thin grey or skin-coloured wavy burrows
- Small papules and vesicles in finger web spaces, wrists, elbows, axillae, waist, umbilicus, buttocks and genitals
- Itchy nodules on the penis and scrotum in men and around the nipples in women
- Thick grey scaly crusts on hands, feet and elsewhere, sometimes with little itch, in crusted scabies
Diagnosis
- Clinical
- Usually clinical: nocturnal itch, typical distribution, burrows and itchy contacts. Standardised criteria (such as IACS 2020) grade the diagnosis as confirmed, clinical or suspected.
- Tests
- Skin scraping of a burrow under mineral oil, examined by microscope, to show mites, eggs or faeces; dermoscopy can show the mite as a dark triangular 'delta wing' at the end of a burrow. A negative scraping does not exclude scabies.
- Imaging
- Not needed.
Differential diagnosis
- Atopic dermatitis and contact dermatitis
- Insect bites and papular urticaria
- Impetigo or folliculitis
- Dermatitis herpetiformis
- Psoriasis (for crusted scabies)
Goal of treatment
Kill the mites in the patient and all close contacts at the same time, prevent re-infestation from clothes and bedding, control itch and treat secondary infection; in institutions, control the outbreak.
Treatment
- Medical
- Topical permethrin, applied to the whole body from the neck down (including the scalp and face in infants) and usually repeated after 1 week, is the first-line scabicide; oral ivermectin is an alternative and is used in mass drug administration in endemic communities.
- Medical
- Crusted scabies: oral ivermectin combined with a topical scabicide and keratolytics, with treatment of all contacts and staff.
- Follow-up
- Itch can last 2–4 weeks after successful treatment; persistent new lesions suggest failure or re-infestation. Nurses watch for secondary infection and check that all contacts were treated.
- Conservative
- Treat all household and sexual contacts at the same time even without symptoms; wash clothes, towels and bedding in hot water or seal them in a plastic bag for at least 72 hours. In hospitals and care homes: contact precautions with gloves and gowns until after effective treatment, and dedicated equipment.
Drugs for this condition
Complications
- Secondary bacterial infection (impetigo, cellulitis, abscess) with Staphylococcus aureus or Streptococcus pyogenes
- Post-streptococcal glomerulonephritis and, in endemic areas, possible links to rheumatic heart disease
- Sepsis, especially in crusted scabies
- Sleep loss, eczematisation and post-scabies nodules
Prognosis
With correct treatment of the patient and contacts, cure is the rule, although itch may persist for weeks. Crusted scabies is harder to eradicate and carries real mortality from secondary sepsis.
Prevention
- Simultaneous treatment of every close contact
- Early recognition and isolation with contact precautions in institutions
- Mass drug administration in highly endemic communities, as promoted by WHO
Test yourself
Think of the answer, then tap the question to see it.
Which mite causes scabies and where does it live in the skin?
Sarcoptes scabiei var. hominis, which burrows into the stratum corneum of the epidermis.
Where are the classic sites of scabies in adults?
Finger web spaces, wrists, elbows, axillae, waist, umbilicus, buttocks and genitals, with nocturnal itch.
What is the first-line topical treatment for scabies?
Permethrin applied to the whole body from the neck down, usually repeated after one week; oral ivermectin is an alternative.
What isolation precautions apply to a hospital patient with crusted scabies?
Contact precautions (gloves and gown, dedicated equipment) until after effective treatment, plus treatment of exposed contacts and staff.
Why does itch continue after successful scabies treatment?
The hypersensitivity reaction to dead mites and their products takes 2–4 weeks to fade.
Related conditions
- Impetigo
- HIV infection and AIDS
- Contact dermatitis (irritant and allergic)
- Cellulitis of the leg
- Sepsis and septic shock
- Rheumatic heart disease
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Scabies (World Health Organization, 2023); Clinical Care of Scabies (Centers for Disease Control and Prevention (CDC), 2024); Scabies (MedlinePlus (U.S. National Library of Medicine), 2024).
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Representative model, for educational purposes only.
