Scabies Treatment: Topical Permethrin as First-Line Therapy
Apply permethrin 5% cream from the neck down (including scalp in infants and elderly), leave on for 8-14 hours, then wash off—this single application is generally curative for uncomplicated scabies. 1, 2
First-Line Treatment Protocol
- Permethrin 5% cream is the CDC-recommended first-line topical treatment for uncomplicated scabies, requiring approximately 30 grams for an average adult 1, 2
- Apply thoroughly to all skin surfaces from the neck down, massaging into the skin 2
- In infants, young children, and geriatric patients, also treat the scalp, hairline, neck, temple, and forehead since these areas are commonly infested in these age groups 1, 2
- Leave the cream on for 8-14 hours before washing off with shower or bath 1, 2
- One application is generally curative, though a second application may be given 7-10 days later if needed 2
Alternative Treatment: Oral Ivermectin
- Oral ivermectin 200 μg/kg (repeated in 2 weeks) serves as an effective alternative first-line option 1, 3
- Take ivermectin with food to increase bioavailability and epidermal penetration 1
- Avoid in children weighing less than 15 kg due to potential neurotoxicity 3
- The two-dose schedule addresses ivermectin's limited ovicidal activity 1
Special Populations
- Pregnant and lactating women: Use permethrin 5% cream as the preferred treatment due to limited safety data for ivermectin 3
- Infants under 2 months: Use permethrin only—avoid ivermectin and lindane due to neurotoxicity risk 3
- Immunocompromised patients require closer monitoring as they face increased risk of treatment failure 1
Crusted (Norwegian) Scabies: Aggressive Combination Therapy Required
- Use combination therapy: topical permethrin 5% cream applied daily for 7 days, then twice weekly PLUS oral ivermectin 200 μg/kg on days 1,2,8,9, and 15 1, 3
- Single-application permethrin or single-dose ivermectin alone will fail in crusted scabies due to the massive mite burden (thousands to millions of mites) 1
- Never skip the oral ivermectin component—topical therapy alone is insufficient 1
Environmental Decontamination and Contact Management
- Machine wash and dry all bedding, clothing, and towels using hot cycles, or dry-clean, or remove from body contact for at least 72 hours 1, 4
- Fumigation of living areas is unnecessary 1
- Examine and treat all sexual, close personal, and household contacts within the preceding month simultaneously, even if asymptomatic 1, 3
Follow-Up and Persistent Symptoms
- Pruritus and rash may persist for up to 2 weeks after successful treatment—this is NOT treatment failure 1, 4, 2
- Persistent pruritus alone is rarely a sign of treatment failure and is not an indication for retreatment 2
- Retreatment is indicated only if live mites are observed after 14 days or symptoms persist beyond 2 weeks 1, 2
- Reevaluate at 2 weeks post-treatment if symptoms continue 1
Critical Pitfalls to Avoid
- Never use lindane in children <10 years, pregnant/lactating women, or persons with extensive dermatitis due to neurotoxicity risk 1, 3
- Avoid using lindane after bathing, which increases absorption and toxicity 1
- Failure to treat all close contacts simultaneously is a common cause of treatment failure and reinfection 1
- Do not expect immediate symptom resolution—allow 2 weeks for post-treatment pruritus to resolve 1, 2
- Inadequate application of topical treatments (missing body areas) leads to treatment failure 1
Emerging Evidence on Permethrin Resistance
- A 2024 randomized controlled trial found permethrin 5% achieved only 27% cure rate compared to 87% for benzyl benzoate 25%, suggesting potential permethrin resistance in some populations 5
- However, current CDC guidelines still recommend permethrin 5% as first-line therapy, and benzyl benzoate is not included in U.S. recommendations though used internationally 1, 4
- If treatment failure occurs with permethrin, consider switching to oral ivermectin or benzyl benzoate where available 4, 5