This post will not make you itchy. Hopefully. Most patients you will see with scabies will present with a pruritic rash of an uncertain etiology. The way that this rash manifests differs depending on the age of the child, and in general, because treatment is benign you should have a low threshold to treat if you think it might possibly, sort of be scabies.
What is it? How common is it?
The etiology is the mite Sarcoptes scabiei. It effects 100 million people worldwide. You will absolutely see it in the Emergency Department. Transmission occurs through direct and prolonged skin-to-skin contact like close familial contacts and sexual partners. It is less likely that someone will contract scabies through contact with clothing or bedding. Crusted scabies is more likely to result in transmission.
How does it present? How do you know that it is scabies and not something else?
The most common locations of lesions are generally intertriginous areas:
- Groin & genitalia
- The “belt line”
- The sides and webs of fingers
In babies the scabies rash can be more diffuse and often spread to the face and scalp. The classic burrow lesion is something that is actually not seen that often in children in my experience. It is pictured below.
More often you will see scattered lesions, some slightly erythematous, others erythematous and scabbed. They are all intensely pruritic.
The diagnosis should be expected on history and physical examination alone. Per the CDC “the diagnosis of scabies should be confirmed by a skin scraping that includes observing the mite, eggs, or mite feces (scybala) under a microscope.”
How do you treat scabies?
Scabies is generally easy to treat. This is the most common regimen:
Permethrin 5% cream (Elimite)
- After bathing or showering, apply cream from the neck (children <5 years apply to head and neck as well) to the soles of the feet paying particular attention to areas that are most involved
- Wash off after 8 to 14 hours
- Repeat in 1 week
- Side effects are itching and stinging
Other treatment considerations and options:
- Permethrin can be applied to infants >2 months of age
- Crusted scabies (which is often seen in immunocompromised patients) requires more aggressive treatment. q2-3d for 1 to 2 weeks – Often in conjunction with oral Ivermectin.
- Ivermectin is not technically FDA approved – 200 to 250 μg/kg PO as single dose and repeated in 1 week
- Crotamiton (Eurax) 10% creams applied from the neck down for 24 hours, rinsed off, then reapplied for an additional 24 hours, and finally washed off.
- Lindane 1% lotion – Apply to all skin surfaces from the neck down and wash off 6 to 8 hours later. Two applications 1 week apart are sufficient, any more frequently runs the risk of neurotoxicity in patients with a seizure disorder.
Following treatment lesions regress in 1-2 days. The significance of itching declines rapidly as well. Though in some, mild pruritic and subtle eczematous skin lesions may last 6 weeks.
Per the CDC “infested persons and their contacts must be treated at the same time to prevent reinfestation.” Patients may feel stigmatized – like they are dirty humans. Let them know that scabies is common, easily treated and does not reflect their fastidiousness and cleanliness as a caregiver.