A 28-year-old woman presents with intense pruritus, particularly worse at night, for the past 3 weeks. She reports similar symptoms in her 5-year-old son and husband. On examination, she has erythematous papules and burrows on the interdigital spaces, wrists, axillae, and lower abdomen. The rest of the family is asymptomatic. Which of the following is the most appropriate initial management?

Explanation

## Diagnosis and Rationale **Key Point:** Scabies is a highly contagious infestation caused by *Sarcoptes scabiei* that spreads through prolonged skin-to-skin contact, making household-wide treatment essential even if asymptomatic. ## Management Principles ### Why Household Treatment is Mandatory - Scabies spreads to close contacts (family members) before symptoms appear, often within 2–6 weeks of exposure. - Asymptomatic family members harbour mites and will develop symptoms if left untreated. - Failure to treat all household contacts leads to re-infestation cycles. ### First-Line Treatment: Topical Permethrin | Parameter | Details | |-----------|----------| | **Agent** | Permethrin 5% cream | | **Application** | Apply to entire body surface (neck to toes, including intertriginous areas) | | **Timing** | Leave on for 8–14 hours (typically overnight) | | **Repeat** | After 7 days (to kill newly hatched mites) | | **Advantage** | Safe in pregnancy, infants >2 months, and breastfeeding | **High-Yield:** The 7-day repeat application is critical because the first application kills adult mites and nymphs but may not reliably kill eggs; the second application targets newly emerged mites. ### Why Other Options Are Suboptimal **Clinical Pearl:** Treating only symptomatic members leaves asymptomatic carriers untreated, perpetuating transmission within the household. - **Ivermectin (oral):** Reserved for crusted scabies, immunocompromised patients, or when topical therapy is impractical; not first-line for typical scabies in an immunocompetent family. - **Sulfur ointment:** Slower acting, requires daily application for 5–7 days, and is less effective than permethrin; reserved for infants <2 months and pregnant women. - **Localized application only:** Scabies is a systemic infestation; burrows and mites can be present on any body surface, including the scalp, genitalia, and soles. ## Post-Treatment Advice 1. Wash all bedding, towels, and clothing in hot water (>60°C) and dry at high heat. 2. Items that cannot be washed should be sealed in a plastic bag for ≥72 hours. 3. Pruritus may persist for 2–4 weeks post-treatment due to residual inflammation; antihistamines or topical steroids may be used. 4. Patients should be reviewed at 2 weeks to assess treatment response and retreat if necessary. **Warning:** Secondary bacterial infection (impetigo) is common due to scratching; educate the patient on avoiding excoriation and consider prophylactic antiseptic measures.