Sarcoptes scabiei infestation. Intense pruritus worse at night, burrows in interdigital webs, wrists, axillae, areolae, genitalia. Infants often have head/neck/palms/soles involvement (unlike older children). Treat patient AND all close contacts simultaneously.
🚩 Red-flag clues (must not miss)
- •Crusted (Norwegian) scabies — heavy infestation in immunocompromised, hyperkeratotic, highly contagious
- •Bullous lesions in infant — atypical presentation
- •Secondary bacterial superinfection (impetiginized) — risk of post-strep glomerulonephritis
Exam
- Burrows (linear, threadlike) in webs/wrists/genitals
- Vesiculopustules on palms/soles in infants
- Family members with similar itch
Differential & next step
| Diagnosis | Clue | Next step |
|---|---|---|
| Scabies | — | Permethrin 5% |
| Atopic dermatitis | Flexural, chronic | Emollients + TCS |
| Contact dermatitis | Match exposure | Avoid trigger |
| Insect bites / papular urticaria | Exposed areas, asymmetric | Antihistamine |
| Tinea | Annular, scaly | Topical antifungal |
Medications & dosing
| Drug | Dose | Notes |
|---|---|---|
| Permethrin 5% cream | Apply head-to-toe (include scalp/face in infants), wash off in 8–14 h; repeat in 7 d | First-line all ages > 2 mo (off-label use < 2 mo with caution) |
| Ivermectin PO | 200 mcg/kg PO ×1, repeat in 7 d | ≥ 15 kg; useful for crusted scabies, outbreaks, treatment failure. Avoid in pregnancy / breastfeeding |
| Antihistamine | Cetirizine 2.5–10 mg PO daily by age | Itch may persist 2–4 weeks post-treatment |
| Topical steroid (post-treatment itch) | Hydrocortisone 1% BID PRN |
Management / next steps
- Treat patient + all household contacts simultaneously
- Wash all bedding, towels, clothing in hot water; bag non-washables × 72 h
- Pruritus may persist 2–4 wk after successful Rx — does not mean failure
- Crusted scabies: combo permethrin + oral ivermectin, isolate, treat all contacts