What is the recommended treatment regimen for scabies, including first‑line therapy, alternatives for infants, pregnant or lactating women, and management of crusted scabies?

Scabies Treatment Guidelines

First-Line Therapy for Uncomplicated Scabies

Permethrin 5% cream is the recommended first-line treatment for uncomplicated scabies in most patients. 1 Apply it to all areas of the body from the neck down and wash off after 8-14 hours. 1 A single application is generally curative. 2

Oral ivermectin (200 μg/kg) is an equally effective first-line alternative, repeated in 2 weeks. 1 Ivermectin must be taken with food to increase bioavailability and epidermal penetration. 1 This oral option is particularly useful when topical application is impractical or in institutional outbreaks. 1

Special Populations

Infants and Young Children

Permethrin 5% cream is the preferred treatment for all pediatric patients, including infants. 2

• Infants and children ≤2 years require whole-body application including the scalp, hairline, forehead, temples, and neck (unlike the neck-down application in adults). 2
• Ivermectin is contraindicated in children weighing <15 kg or younger than 10 years due to potential blood-brain barrier penetration and neurotoxicity. 2
• Never use lindane in children <10 years because of high seizure and neurotoxicity risk. 2

Pregnant and Lactating Women

Permethrin 5% cream is the only recommended treatment for pregnant or lactating women. 1, 2 Ivermectin lacks sufficient safety data in pregnancy and breastfeeding, making it unsuitable despite being "low-risk" based on limited human data. 3, 1

Crusted (Norwegian) Scabies

Crusted scabies requires aggressive combination therapy with both topical and oral agents. 1 This severe form harbors thousands to millions of mites and is far more contagious than typical scabies. 1

The treatment regimen includes:

• Topical permethrin 5% cream applied daily for 7 days, then twice weekly until cure 1
• Plus oral ivermectin 200 μg/kg on days 1,2,8,9, and 15 1
• Mandatory specialist consultation for management 1

Single-application permethrin as used for ordinary scabies will fail in crusted scabies. 1 The multiple-dose ivermectin schedule addresses the drug's limited ovicidal activity and the massive mite burden. 1

Alternative Treatments (When Permethrin Unavailable or Fails)

• Sulfur 6% ointment applied nightly for 3 consecutive nights (wash off before each reapplication) 1
• Lindane 1% applied for 8 hours 1, but avoid in children <10 years, pregnant/lactating women, and persons with extensive dermatitis due to neurotoxicity risk 3, 1
• Crotamiton 10% cream applied nightly for 2 nights, washed off 24 hours after the second application (approximately 60% cure rate versus 89% for permethrin) 2

Management of Contacts and Environment

All household members, close contacts, and sexual partners within the preceding month must be treated simultaneously, even if asymptomatic. 1, 2 Failure to treat contacts simultaneously is the most common cause of treatment failure. 4

Decontaminate bedding, clothing, and towels by:

• Machine washing and drying using hot cycles 1
• Dry cleaning 1
• Or removing from body contact for at least 72 hours (mites cannot survive off-host longer than this) 1, 2

Fumigation of living areas is unnecessary. 1

Follow-Up and Retreatment Criteria

Pruritus and rash may persist for up to 2 weeks after successful treatment due to allergic dermatitis, not treatment failure. 3, 1 This is a critical point to avoid unnecessary retreatment.

Retreatment is indicated only if:

• Symptoms persist beyond 2 weeks AND live mites are observed 3, 1
• New lesions continue to appear 2

When retreatment is needed, use an alternative regimen rather than repeating the same failed therapy. 3

Institutional Outbreak Management

During outbreaks in nursing homes or other institutions, treat the entire at-risk population simultaneously. 3, 5 Mass oral ivermectin is recommended for ease of administration in these settings. 3 Outbreak response should involve specialist consultation to coordinate treatment and control measures. 3

Common Treatment Pitfalls to Avoid

• Not repeating the ivermectin dose at 2 weeks is essential for complete eradication 4
• Using lindane after bathing increases absorption and toxicity risk 1
• Inadequate application of topical treatments (missing under nails, body orifices) leads to treatment failure 4
• Applying corticosteroids during active treatment can suppress inflammatory response and allow mites to proliferate 1
• Expecting immediate symptom resolution when post-treatment pruritus can persist 2 weeks 3, 1