Your 10-year-old daughter has an itchy rash on her wrist and hands. She has scratched the area so badly that it is starting to scab, but she says it is still extremely itchy. You’ve tried lotions and creams but the itch is still there, and now the rash has spread to her tummy and legs. Your pediatrician diagnoses scabies. Scabies?
Scabies is a skin inflammation caused by the insect Sarcoptes scabiei, a mite so tiny it cannot be seen with the naked eye. The female mite burrows into the skin, lays her eggs and moves on to other areas or other people. Over a period of weeks, the eggs hatch and the mites spread. The material left by the mites causes an inflammatory rash, which is almost always described as intensely itchy.

The rash can appear as long burrows or tunnels just at the surface of the skin, or as skin-colored bumps, located in the webs between fingers, at the wrists, at the outside of the elbows and other places. In babies, scabies can appear in the diaper area, on the trunk and all along the arms and legs.

A doctor usually makes the diagnosis of scabies just by looking at the rash. It is possible to scrape one of the burrows and find the insect or eggs by looking at the scraping under the microscope — but 90 percent of the time the scraping doesn’t show the mites.

Although scabies alarms most of us who prefer not to think of insects burrowing into our skin, scabies does respond well to treatment. The best treatment is to apply a cream of 5-percent permethrin (Acticin, Elimite), an insecticide, to the child’s body — all of it, from the neck down — and leave it on overnight, for eight to 14 hours. Be sure not to apply it to the fingers of young children if they suck their thumbs or fingers.

The next morning, bathe or shower the child to remove the insecticide, and then launder the child’s sheets, towels and all clothing worn recently. One permethrin treatment is all that is needed in most cases. Even though the insecticide kills the mites, itching can remain for a few days or even weeks because the remaining insect products cause inflammation. Twice daily application of 0.5-percent hydrocortisone cream (available over the counter) to the itchiest skin can ease the inflammation, and oral diphenhydramine (Benadryl and other over-the-counter products) reduces the itching.

As an alternative, you can apply 1-percent gamma benzene hexachloride (Lindane) lotion, but there is concern that the skin of young children may absorb this product, which can be toxic to the nervous system.

Crotamiton (Eurax), a non-insecticide, is sometimes prescribed but is less effective than either permethrin or gamma benzene hexachloride.

Scabies are spread by contact with others, especially when children sleep in the same bed or play closely together. If one child in the family is diagnosed with scabies, it is wise to treat others in the family (including adults) who are very itchy or have a similar rash. Your pediatrician will have other suggestions for you and your family if the scabies seems particularly troublesome or recurs.

Dr. Carole A. Stashwick is a pediatrician and an associate professor of pediatrics at Dartmouth Medical School, where she also director of the pediatric residency program.