What is the recommended treatment for a patient with scabies, considering potential skin conditions or allergies?

Scabies Treatment

Permethrin 5% cream is the first-line treatment for scabies in most patients, applied from the neck down for 8-14 hours, with oral ivermectin 200 μg/kg (repeated in 2 weeks) as an equally effective alternative, particularly useful for institutional outbreaks or patients unable to apply topical therapy. 1, 2

First-Line Treatment Options

Permethrin 5% Cream (Preferred for Most Patients)

• Apply to all body areas from neck down and wash off after 8-14 hours 3, 1, 2
• More effective, safer, and less expensive than ivermectin for standard scabies 3, 1
• Generally curative with one application in 92.5-94.2% of patients 4, 5
• For infants, elderly, and immunocompromised patients: apply scalp-to-toes including hairline, neck, temple, and forehead 1

Oral Ivermectin (Alternative First-Line)

• Dosage: 200 μg/kg body weight, must repeat in 2 weeks 3, 1, 2
• Take with food to increase bioavailability and epidermal penetration 3, 1, 2
• The second dose is essential because ivermectin has limited ovicidal activity and does not kill eggs present at initial treatment 3, 1
• Cure rate: 85.9% at 2 weeks, reaching 100% after retreatment 5
• No dosage adjustments needed for renal impairment, but safety uncertain in severe liver disease with multiple doses 3

Special Populations

Pregnant and Lactating Women

• Permethrin 5% cream is the preferred treatment 3, 1, 4
• Ivermectin is classified as "human data suggest low risk" in pregnancy and probably compatible with breastfeeding 3, 1
• Avoid lindane completely—associated with neural tube defects and mental retardation 3

Infants and Children

• Permethrin is recommended for all infants and young children 3, 1, 4
• Ivermectin not recommended for children weighing <15 kg due to potential neurotoxicity 4
• Permethrin safe and effective in infants ≥2 months old 6
• For infants <2 months: use permethrin only, applied scalp-to-toes 4
• Children <10 years must avoid lindane due to neurotoxicity risk 3, 1, 4

Patients with Extensive Dermatitis or Skin Conditions

• Use permethrin or ivermectin; avoid lindane completely 3, 1
• Lindane absorption increases with extensive dermatitis, raising seizure risk 3, 1

Alternative Treatment Options (When First-Line Fails or Unavailable)

Lindane 1% (Last Resort Only)

• Apply thinly from neck down, wash off after 8 hours 3, 1
• Only use if patient cannot tolerate recommended therapies or these have failed 3
• Never use immediately after bathing—increases absorption and seizure risk 3, 1
• Contraindicated in: children <10 years, pregnant/lactating women, extensive dermatitis 3, 1, 4

Sulfur 6% Ointment

• Apply nightly for 3 consecutive nights, washing off previous applications before reapplying 1
• One recent study showed 10% sulfur ointment significantly more effective than permethrin (p<0.001), though this contradicts established guidelines and may reflect permethrin resistance 7

Crotamiton 10%

• Apply nightly for 2 consecutive nights, wash off 24 hours after second application 1, 8

Crusted (Norwegian) Scabies

Requires aggressive combination therapy—single-agent treatment will fail 1, 2

• 5% permethrin cream applied daily for 7 days, then twice weekly until cure 1, 2, 4
• PLUS oral ivermectin 200 μg/kg on days 1,2,8,9, and 15 1, 2, 4
• The multiple-dose ivermectin schedule addresses limited ovicidal activity and massive mite burden 2
• Never use single-application permethrin or oral ivermectin alone—this will fail 2

Environmental and Contact Management

Decontamination (Critical to Prevent Reinfection)

• Machine wash and dry all bedding, clothing, and towels using hot cycle, or dry clean 3, 1, 2
• Alternatively, remove items from body contact for at least 72 hours (mites cannot survive off human host) 3, 1, 2
• Fumigation of living areas is unnecessary 3, 1, 2
• Vacuum furniture and carpets 9

Contact Tracing and Treatment

• Examine and treat all persons with sexual, close personal, or household contact within the preceding month 3, 1, 2, 4
• Treat all contacts simultaneously, even if asymptomatic, to prevent reinfection 1, 4
• For institutional outbreaks, treat the entire at-risk population and consult an expert 1

Follow-Up and Management of Persistent Symptoms

Expected Post-Treatment Course

• Pruritus may persist for up to 2 weeks after successful treatment—this is normal sensitization reaction, not treatment failure 1, 2, 4
• Approximately 75% of patients with pruritus at 2 weeks have resolution by 4 weeks 6

When to Retreat

• Evaluate after 1 week if symptoms persist 3, 1
• Consider retreatment after 2 weeks only if: live mites observed, symptoms persist beyond 2 weeks, or other signs of treatment failure 1, 2, 4
• Persistent pruritus alone is NOT an indication for retreatment 1

Reasons for Treatment Failure

• Resistance to medication (emerging concern with permethrin) 1, 7
• Faulty application of topical treatments (most common) 1, 9
• Reinfection from untreated contacts or fomites 1, 9
• Failure to treat face and scalp in high-risk populations 9

Critical Treatment Pitfalls to Avoid

• Failure to treat all close contacts simultaneously 1, 2
• Inadequate application of topical treatments (missing face/scalp in infants, elderly, immunocompromised) 1, 9
• Using lindane after bathing or in contraindicated populations 3, 1, 4
• Not repeating ivermectin dose after 2 weeks 1, 2
• Expecting immediate resolution of symptoms—may take up to 2 weeks 1, 2
• Using topical corticosteroids during active treatment phase—suppresses inflammatory response and may allow mites to proliferate 2
• Failure to decontaminate bedding and clothing 3, 1, 9

Use of Adjunctive Corticosteroids

• Only consider triamcinolone or other topical corticosteroids if pruritus persists beyond 2 weeks AND after confirming no live mites present 2
• Never use during active treatment phase—can suppress identification of active infestation 2
• Apply only to limited affected areas to minimize risks of atrophy, pigmentary changes, and telangiectasias 2