Scabies: Clinical Presentation and Management
First-Line Treatment
Permethrin 5% cream is the gold standard treatment for uncomplicated scabies, applied to all areas of the body from the neck down and washed off after 8-14 hours. 1, 2, 3
Application Protocol
- Apply to entire body surface from neck to soles of feet (including under fingernails) 3
- In infants, young children, and geriatric patients, also treat the scalp, hairline, neck, temple, and forehead 3
- Leave on for 8-14 hours before washing off 1, 3
- Approximately 30 grams is sufficient for an average adult 3
- One application is generally curative 3
Alternative First-Line Option
- Oral ivermectin 200 μg/kg body weight, taken with food, repeated in 2 weeks 1, 2
- Taking with food increases bioavailability and epidermal penetration 1
- No dosage adjustment needed for renal impairment 1
Special Populations
Pregnant and Lactating Women
Infants and Children
- Permethrin 5% cream is safe for children ≥2 months of age 3
- Must treat scalp, temple, and forehead in addition to body 3
- Never use lindane in children <10 years due to seizure risk 1, 2
Immunocompromised Patients
Crusted (Norwegian) Scabies
This severe form requires aggressive combination therapy, not single-agent treatment. 1
Treatment Protocol
- Topical: 5% permethrin cream applied daily for 7 days, then twice weekly until cure 1, 2
- Oral: Ivermectin 200 μg/kg on days 1,2,8,9, and 15 1, 2
- Take ivermectin with food 1
- Single-application permethrin will fail 1
- Topical therapy alone is insufficient given massive mite burden 1
Alternative Treatments (When First-Line Options Unavailable)
Lindane 1%
- Apply thinly from neck down, wash off after 8 hours 4, 2
- Contraindications: 4, 1, 2
- Children <10 years
- Pregnant or lactating women
- Persons with extensive dermatitis
- Never apply after bathing (increases absorption and seizure risk)
- Resistance reported in some U.S. regions 4
Other Alternatives
- Crotamiton 10%: Apply nightly for 2 consecutive nights, wash off 24 hours after second application 4
- Sulfur 6% ointment: Apply nightly for 3 nights 2
Contact Management
All close contacts must be treated simultaneously, even if asymptomatic. 1, 2
Who to Treat
- All sexual partners within the preceding month 4, 5
- All household members and close personal contacts within the preceding month 4, 1, 2
- For institutional outbreaks, treat entire at-risk population 2
Environmental Decontamination
Required Measures
- Machine wash and dry bedding/clothing using hot cycle 4, 2, 5
- Alternatively: dry clean or remove from body contact for ≥72 hours 4, 2, 5
- Fumigation of living areas is unnecessary 4, 2, 5
- Keep fingernails closely trimmed 2
Follow-Up and Expected Course
Normal Post-Treatment Symptoms
- Pruritus may persist for up to 2 weeks after successful treatment 1, 2, 3
- This is NOT a sign of treatment failure 3
- Approximately 75% of patients with persistent pruritus at 2 weeks will have resolution by 4 weeks 3
When to Retreat
- Retreat if live mites are observed after 14 days 3
- Consider retreatment if symptoms persist beyond 2 weeks 1, 2
- Evaluate at 1 week if symptoms worsen 4
Common Treatment Failures and How to Avoid Them
Critical Pitfalls
- Failure to treat all close contacts simultaneously (most common cause of reinfection) 1, 2
- Inadequate application of topical treatments (missing areas like finger webs, under nails, genitalia) 1, 2
- Using lindane after bathing (increases absorption and seizure risk) 1, 2
- Not repeating ivermectin dose after 2 weeks 1, 2
- Expecting immediate symptom resolution (pruritus can persist 2 weeks) 1, 2
- Failure to decontaminate fomites 2
- Using single-dose therapy for crusted scabies 1
Reasons for Persistent Symptoms
- Treatment failure or medication resistance 2
- Reinfection from untreated contacts 1, 2
- Reinfection from contaminated fomites 1, 2
- Cross-reactivity with other household mites 1, 2
- Normal post-treatment inflammatory response 3
Clinical Vignettes
Vignette 1: Classic Scabies
Presentation: 28-year-old woman presents with 3 weeks of intensely pruritic rash, worse at night. Examination reveals erythematous papules on finger webs, wrists, axillae, and inframammary folds. Linear burrows visible on wrists.
Management:
- Apply permethrin 5% cream to entire body from neck down 1, 3
- Leave on 8-14 hours, then wash off 3
- Treat sexual partner from past month simultaneously 4, 5
- Machine wash all bedding/clothing in hot water 2
- Counsel that itching may persist 2 weeks 1, 3
- Repeat treatment in 7-10 days if symptoms persist 4
Vignette 2: Pregnant Patient
Presentation: 32-year-old woman at 24 weeks gestation with pruritic rash on hands, wrists, and abdomen for 2 weeks. Husband recently treated for scabies.
Management:
- Use permethrin 5% cream only (avoid lindane and ivermectin) 4, 2, 5
- Apply from neck down for 8-14 hours 3
- Treat all household contacts simultaneously 2
- Decontaminate environment 2
Vignette 3: Crusted Scabies in HIV Patient
Presentation: 45-year-old man with AIDS (CD4 50) presents with thick, crusted plaques on hands, feet, and trunk. Minimal pruritus. Widespread scaling.
Management:
- Combination therapy required 1, 2
- Permethrin 5% cream daily × 7 days, then twice weekly until cure 1
- Oral ivermectin 200 μg/kg on days 1,2,8,9, and 15 (with food) 1
- Isolate patient until after second ivermectin dose 1
- Aggressive environmental decontamination 2
- Single-agent therapy will fail 1
Vignette 4: Infant with Scabies
Presentation: 6-month-old infant with irritability and pruritic rash on palms, soles, and scalp. Mother has similar rash.
Management:
- Permethrin 5% cream is safe ≥2 months of age 3
- Must include scalp, temple, and forehead 3
- Treat mother simultaneously 2
- Avoid lindane (contraindicated <10 years) 1, 2
- Wash all clothing and bedding in hot water 2
Vignette 5: Nursing Home Outbreak
Presentation: Multiple residents in skilled nursing facility with pruritic rash over 3 weeks.
Management: