Skin Mite Presentation and Treatment
Clinical Presentation of Scabies
Scabies presents with intense pruritus (itching) that worsens at night, accompanied by a characteristic papular rash with burrows, typically affecting web spaces between fingers, wrists, elbows, axillae, waistline, and genitalia. 1, 2
- In infants and elderly patients, the scalp, hairline, neck, temple, and forehead may be infested, unlike typical adult presentations 3
- Pruritus, edema, and erythema are common accompanying symptoms that may temporarily worsen after treatment initiation 3
First-Line Treatment: Permethrin 5% Cream
The CDC recommends permethrin 5% cream as the first-line topical treatment for uncomplicated scabies. 1, 2
Application Protocol:
- Apply thoroughly from the neck down to the soles of the feet (approximately 30 grams for an average adult) 3
- In infants and geriatric patients, also treat the scalp, temple, and forehead 3
- Leave on for 8-14 hours, then wash off 1, 2, 3
- One application is generally curative 2, 3
Special Populations:
- Permethrin is the preferred treatment for pregnant/lactating women, infants, and young children due to its safety profile 1, 2
- Safe and effective in pediatric patients two months of age and older 3
Alternative First-Line Treatment: Oral Ivermectin
Oral ivermectin 200 μg/kg is an effective alternative, repeated in 2 weeks. 1, 2
Key Administration Details:
- Must be taken with food to increase bioavailability and epidermal penetration 1
- Contraindicated in children weighing less than 15 kg due to neurotoxicity risk 2
- Not recommended for pregnant or lactating women due to limited safety data 2
- No dosage adjustments needed for renal impairment 1
Comparative Efficacy:
- Two applications of permethrin (one week apart) achieved 96.9% cure rate versus 62.4% with single-dose ivermectin, increasing to 92.8% with two doses 4
- Recent 2023 data shows topical ivermectin 1% achieved 85.5% cure rate versus 89.9% with permethrin 5%, with no statistically significant difference 5
Crusted (Norwegian) Scabies
Combination therapy is required for crusted scabies: 1, 2
- Topical 5% permethrin cream applied daily for 7 days, then twice weekly until cure 1
- PLUS oral ivermectin 200 μg/kg on days 1,2,8,9, and 15 1, 2
Contact and Environmental Management
All close personal, sexual, or household contacts within the preceding month must be examined and treated simultaneously, even if asymptomatic. 1, 2
- Failure to treat contacts simultaneously is the most common cause of treatment failure 1
- Decontaminate bedding and clothing by machine washing/drying on hot cycle, dry cleaning, or removing from body contact for at least 72 hours 1
- Fumigation of living areas is unnecessary 1
Follow-Up and Persistent Symptoms
Rash and pruritus may persist for up to 2 weeks after successful treatment and does not indicate treatment failure. 1, 2, 3
- In clinical trials, approximately 75% of patients with persistent pruritus at 2 weeks had resolution by 4 weeks 3
- Consider retreatment only if symptoms persist after 2 weeks AND live mites are observed 1, 2, 3
- Persistent symptoms may result from treatment failure, reinfection from untreated contacts, or cross-reactivity with other household mites 1
Critical Pitfalls to Avoid
Common treatment failures occur from: 1
- Failing to treat all close contacts simultaneously
- Inadequate application of topical treatments (missing under nails, body orifices)
- Not repeating ivermectin dose at 2 weeks
- Using lindane after bathing (increases absorption and neurotoxicity risk) 1, 2
Avoid lindane in children <10 years, pregnant/lactating women, and persons with extensive dermatitis due to neurotoxicity risk. 1, 2
Demodicosis (Demodex Mites)
While the provided evidence focuses primarily on scabies, topical ivermectin has demonstrated efficacy for treating Demodex mite infestations 6, though specific protocols differ from scabies treatment and should be guided by clinical presentation.