A 32-year-old woman from rural India presents with intense nocturnal pruritus, linear burrows on the wrists and interdigital spaces, and erythematous papules on the abdomen. Microscopy of skin scrapings confirms *Sarcoptes scabiei*. Regarding the management and complications of scabies, all of the following are correct EXCEPT:

Explanation

## Scabies Management: Drug Choice and Safety ### Key Point: **Benzyl benzoate is NOT preferred in infants and young children — it is actually contraindicated in infants <2 years due to neurotoxicity risk.** Permethrin 5% is the safest first-line choice across all age groups. ### Treatment Hierarchy by Age and Risk | Population | First-line | Alternative | Avoid | |------------|-----------|-------------|-------| | **Adults** | Permethrin 5% | Benzyl benzoate 10% | — | | **Children 2–5 years** | Permethrin 5% | Sulfur 5–10% | Benzyl benzoate, ivermectin | | **Infants <2 years** | Sulfur 5–10% | Permethrin 5% (if needed) | Benzyl benzoate, ivermectin | | **Pregnant women** | Permethrin 5%, sulfur | — | Ivermectin (teratogenic risk) | | **Immunocompromised** | Permethrin 5% (multiple doses) | Ivermectin + permethrin | — | ### High-Yield: **Permethrin 5% cream is the gold standard first-line treatment** for scabies in all age groups except infants <2 years (use sulfur 5–10% instead). It is applied to the entire body surface including scalp, behind ears, and between toes, left on for 8–14 hours, then washed off. ### Clinical Pearl: **Benzyl benzoate 10%** is an older agent that carries risk of neurotoxicity, especially in infants and young children. It is rarely used as first-line in modern practice and is contraindicated in children <2 years and pregnant women. ### Mnemonic: PERM-SAFE - **P**ermethrin → first-line (all ages >2 years) - **E**fficacy → 95%+ cure rate - **R**epeat → apply once, reapply after 1–2 weeks if needed - **M**inutes → leave on for 8–14 hours - **S**ulfur → alternative for infants and pregnant women - **A**void benzyl benzoate in young children - **F**amily → treat all household contacts simultaneously - **E**xcoriation → treat secondary infection separately ### Complications of Scabies | Complication | Mechanism | Prevention | |--------------|-----------|------------| | **Secondary bacterial infection** | Scratching → breach of skin barrier → *S. aureus* or *S. pyogenes* | Early treatment, patient education on not scratching | | **Post-streptococcal glomerulonephritis** | *S. pyogenes* infection → immune complex deposition | Treat bacterial infection promptly with antibiotics | | **Scabies nodosorum** | Hypersensitivity reaction to mite antigens | Rare; treat with topical/intralesional corticosteroids | | **Crusted scabies** | Immunocompromised host → massive mite burden | Requires prolonged/repeated treatment + ivermectin | ### Warning: **Do NOT use benzyl benzoate in infants <2 years** — risk of CNS toxicity. **Do NOT use ivermectin in pregnancy** — teratogenic potential. **Do NOT use permethrin in infants <2 months** — use sulfur instead.