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OverviewAetiologyPathophysiologyClinical features and red flagsInvestigationsDifferential diagnosisManagementComplicationsMonitoring and follow-upSpecial situationsCommon pitfallsQuestionsSources
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Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.

Scabies diagnosis and contact treatment

Dermatology · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

RapidFull

Overview

Recognise ordinary and crusted scabies, confirm uncertain disease, treat the whole skin field correctly, coordinate simultaneous close-contact treatment and distinguish persistent post-scabetic itch from failure.

Take a contact timeline before examining the full distribution with consent. Burrows are easiest at finger webs, wrist creases, sides of hands and genital skin; dermoscopy may show a dark triangular mite at the burrow end. In darker skin, papules may be brown or violaceous and post-inflammatory pigment prominent, while the linear burrow and excoriation remain useful.

Treatment failure usually reflects missed skin, washed-off hands, absent second application, untreated contacts or reinfestation rather than resistance. Give written application instructions and agree one treatment night for the whole contact group. Manage eczema and itch after eradication without reflexively repeating scabicide.

Crusted scabies may appear as psoriasis-like hyperkeratosis on hands, feet, scalp or widespread skin. Mite burden makes it a public-health urgency. Use isolation and personal protective equipment, identify contacts and follow current UKHSA outbreak guidance with specialist oral ivermectin plus repeated topical therapy.

Key points

  • Suspect scabies with new intense nocturnal itch, affected close contacts, burrows and papules at finger webs, wrists, axillae, waist, buttocks, genitalia or areolae.
  • In infants, older people and immune compromise, scalp, face, palms and soles may be involved; crusted scabies can itch little despite huge mite burden.
  • Apply permethrin 5% cream to the complete recommended skin field, including under nails and between digits, leave 8–12 hours and repeat after seven days.
  • Reapply to hands if washed during the contact period and do not miss buttock cleft, genital skin, soles or beneath jewellery.
  • Treat all household and sexual contacts simultaneously even if asymptomatic, because first infestation may not itch for weeks.
  • Wash recently used clothes, towels and bedding hot where possible or seal unwashable items for at least 72 hours according to outbreak advice.
  • Itch can persist four to six weeks after effective treatment; new burrows or new typical lesions are stronger evidence of failure than itch alone.
  • Crusted scabies needs urgent dermatology, infection-control and UKHSA-coordinated combined topical and oral therapy.

Aetiology

01

Sarcoptes infestation

Fertilised Sarcoptes scabiei mites burrow in stratum corneum and spread mainly through prolonged direct skin contact.

02

Close-contact transmission

Household, sexual and hands-on care contacts transmit infestation before symptoms, creating asymptomatic reservoirs unless treated simultaneously.

03

Crusted host state

Immune suppression, frailty, neurological impairment and inability to scratch permit enormous mite burdens and highly contagious crusted scabies.

04

Fomite contribution

Clothing and bedding matter most in crusted disease; ordinary scabies is predominantly contact-spread but recent textiles still enter coordinated control.

Pathophysiology

  1. 1
    Burrow formation

    Female mites tunnel through superficial keratin and lay eggs, creating a fine wavy track with a vesicle or mite at its end.

  2. 2
    Delayed hypersensitivity

    Itch develops weeks after first infestation through immune response to mites and products, while reinfestation can itch much sooner.

  3. 3
    Excoriation and eczema

    Nocturnal scratching produces papules, nodules, dermatitis, crust and secondary bacterial infection that can obscure diagnostic burrows.

  4. 4
    Hyperinfestation

    In crusted scabies, uncontrolled replication creates thick scale packed with mites and makes brief contact or contaminated fomites more infectious.

Clinical features and red flags

Nocturnal contact itch

Severe itch worse in bed with a newly itchy household or sexual contact strongly supports scabies.

Burrow

A short thin wavy grey-brown line with a terminal vesicle is the most specific ordinary scabies lesion.

Genital scabetic nodule

Persistent itchy firm nodules on penis or scrotum are characteristic and may remain after mite eradication.

Crusted scabiesRed flag

Extensive hyperkeratotic scale, fissures and nail debris in a vulnerable host indicates highly infectious hyperinfestation.

Secondary infectionRed flag

Honey crust, spreading warmth, pain, pus or fever suggests bacterial complication requiring separate assessment.

Red flags requiring action

  • Crusted scabies, institutional outbreak, secondary sepsis, pregnancy or infancy with treatment uncertainty, severe immune or neurological impairment, eye exposure or persistent disease after correctly coordinated courses requires specialist or UKHSA support.

Investigations

  1. 01
    Dermoscopy of a burrowFirst step
    Why
    Visualise a mite and guide scraping in uncertain disease.
    Interpretation and limitations
    A triangular mite sign supports diagnosis; negative dermoscopy depends on operator and lesion selection.
  2. 02
    Skin scraping microscopy
    Why
    Demonstrate mite, eggs or faecal pellets in atypical, outbreak or crusted disease.
    Interpretation and limitations
    A positive result confirms infestation, while one negative scraping cannot exclude low-burden ordinary scabies.
  3. 03
    Contact and setting map
    Why
    Define simultaneous household, sexual, care and institutional treatment groups.
    Interpretation and limitations
    Include contact during the infectious interval even without itch; first symptoms are delayed.
  4. 04
    Bacterial culture
    Why
    Assess pus, crust or cellulitis complicating excoriated lesions.
    Interpretation and limitations
    Sample fresh infection before antibiotics and continue scabies eradication alongside bacterial care.
  5. 05
    Immune assessment when indicated
    Why
    Identify a driver of crusted, unusually extensive or refractory disease.
    Interpretation and limitations
    Target HIV, haematological or medicine assessment to the phenotype and obtain consent.

Differential diagnosis

01

Atopic or contact eczema

Chronic flexural dermatitis and a product-related distribution usually lack scabetic burrows and a new household nocturnal-itch cluster.

02

Papular insect-bite reaction

Exposed-site crops with a pet, travel or bedbug pattern differ from burrows in finger webs and genital nodules.

03

Dermatitis herpetiformis

Symmetrical intensely itchy extensor vesicles with a coeliac association require properly sited biopsy and immunofluorescence rather than permethrin.

04

Delusions of infestation

Fixed infestation belief without objective lesions requires respectful dermatological exclusion and mental-health-aware care, not repeated pesticide exposure.

Management

01Ordinary scabiesTreat patient and contacts togetherFirst stepTypical itch, distribution or confirmed mites occurs without crusted disease.+
  1. 1Apply permethrin 5% to the complete age-appropriate skin field for 8–12 hours, reapplying washed hands.
  2. 2Repeat after seven days and treat household and sexual contacts on both dates regardless of symptoms.
  3. 3Decontaminate recent textiles, treat secondary eczema and review new burrows rather than itch alone.
02Crusted or outbreak diseaseActivate infection controlHyperkeratotic high-burden disease or linked institutional cases are suspected.+
  1. 1Isolate appropriately, use protective equipment and notify infection-control and UKHSA teams promptly.
  2. 2Confirm with abundant scale where possible and start specialist combined oral ivermectin and repeated topical treatment.

Complications

01

Bacterial infection

Repeated skin excoriations permit impetigo, cellulitis and occasionally invasive streptococcal or staphylococcal disease with systemic illness.

02

Institutional outbreak

Missed crusted scabies can expose numerous residents, visitors and staff and requires rapid UKHSA-supported infection-control coordination.

03

Persistent nodules and itch

Hypersensitivity can continue for several weeks after successful eradication, particularly in genital nodules, without indicating persistent living mites.

04

Treatment toxicity

Repeated unsupervised scabicide use irritates skin and reinforces itch, obscuring whether correct application and contacts were addressed.

Monitoring and follow-up

  • Check completion of both applications for every contact, including washed-hand reapplication and commonly missed body sites.
  • Review new burrows, new lesions and contact cases at two to four weeks rather than using itch intensity alone.
  • Treat residual dermatitis with emollient and appropriate topical anti-inflammatory care after eradication.
  • Escalate bacterial cellulitis, fever, crusted disease or institutional clustering promptly.
  • Avoid repeated permethrin cycles without examination because irritant dermatitis can perpetuate symptoms.

Special situations

Contacts may feel well

Delayed hypersensitivity means an infested first-time contact can transmit mites for weeks before itching.

Hands undo treatment

Washing during overnight application removes scabicide from a high-burden site unless it is promptly reapplied.

Itch outlives mites

Immune response to mite remnants can persist for weeks and does not alone prove resistance.

Crust means burden

Thick scale in a vulnerable host contains vast mite numbers and changes contact and environmental control.

Common pitfalls

  1. 01

    Treating only the itchy index patient and leaving asymptomatic household contacts infested.

  2. 02

    Applying permethrin to visible spots rather than the complete recommended skin field.

  3. 03

    Forgetting the second application after seven days.

  4. 04

    Repeating scabicide for itch alone and causing irritant dermatitis.

  5. 05

    Missing crusted scabies because a frail patient reports little itch.

Practice

Two practice questions

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Question 1 of 2
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DermatologyOriginal SBA

Itchy household cluster

A patient has nocturnal itch, finger-web burrows and two currently asymptomatic household contacts living in the same home. Which treatment plan is correct?

Choose one answer, then submit
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Sources and review status3 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.

  • UKHSA scabies management adviceCurrent outbreak, crusted disease, contact and environmental control.
  • British Association of Dermatologists scabiesRecognition, application, repeat treatment and post-scabetic itch.
  • Permethrin 5% cream SmPCPermethrin application, age and safety information.

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateComplete draftClinical stateAwaiting reviewJurisdictionUnited Kingdom
3
Coordinate expanded contact treatment and environmental cleaning, continuing until specialist clearance criteria are met.
03Persistent symptomsSeparate itch from live infestationItch remains after two properly timed courses.+
  1. 1Verify full-field application, contact synchrony, hand reapplication, textile measures and any new exposure.
  2. 2Examine for new burrows or active papules and confirm with dermoscopy or scraping before further pesticide use.
  3. 3Treat post-scabetic eczema or nodules symptomatically and refer objectively persistent disease for diagnostic review.
Key medicines and prescribing safety1 treatment · regimens, roles and cautions+
First-line topical scabicide for ordinary scabies and part of combined crusted-scabies regimens.

Permethrin 5% cream

Apply to the entire recommended skin surface, leave for 8–12 hours, wash off and repeat the complete application after seven days.

Avoid eyes and mucosa, reapply after hand washing, use age- and pregnancy-specific advice, and recognise transient burning and persistent post-treatment itch.