Scabies is an itchy skin condition caused by a tiny burrowing mite called Sarcoptes scabiei. Intense itching occurs in the area where the mite burrows. The urge to scratch may be especially strong at night.

Scabies is contagious and can spread quickly through close physical contact in a family, child care group, school class, nursing home or prison. Because scabies is so contagious, doctors often recommend treatment for entire families or contact groups.<

Scabies can be readily treated. Medications applied to your skin kill the mites that cause scabies and their eggs. But you may still have some itching for several weeks after treatment.

Symptoms

Scabies signs and symptoms include:

• Itching, often severe and usually worse at night
• Thin, irregular burrow tracks made up of tiny blisters or bumps on your skin

The burrows or tracks typically appear in folds of skin. Though almost any part of the body may be involved, in adults and older children scabies is most often found:

• Between the fingers
• In the armpits
• Around the waist
• Along the insides of the wrists
• On the inner elbows
• On the soles of the feet
• Around the breasts
• Around the male genital area
• On the buttocks
• On the knees

In infants and young children, common sites of infestation usually include the:

• Scalp
• Palms of the hands
• Soles of the feet

If you’ve had scabies before, signs and symptoms may develop within a few days of exposure. If you’ve never had scabies, it can take as long as six weeks for signs and symptoms to begin. You can still spread scabies even if you don’t have any signs or symptoms yet.

Causes

The eight-legged mite that causes scabies in humans is microscopic. The female mite burrows just beneath your skin and makes a tunnel where it deposits eggs.

The eggs hatch, and the mite larvae work their way to the surface of your skin, where they mature and can spread to other areas of your skin or to the skin of other people. The itching of scabies results from your body’s allergic reaction to the mites, their eggs and their waste.

Close physical contact and, less often, the sharing of clothing or bedding with an infected person can spread the mites.

Animals and humans all are affected by their own distinct species of mites. Each species prefers one specific type of host and doesn’t live long away from that preferred host.

Humans may have a temporary skin reaction from contact with the animal scabies mite. But people are unlikely to develop full-blown scabies from this source, as they might from contact with the human scabies mite.

Complications

Vigorous scratching can break your skin and allow a secondary bacterial infection, such as impetigo, to occur. Impetigo is a superficial infection of the skin that’s caused most often by staph (staphylococci) bacteria or occasionally by strep (streptococci) bacteria.

A more severe form of scabies, called crusted scabies, may affect certain high-risk groups, including:

• People with chronic health conditions that weaken the immune system, such as HIV or chronic leukemia
• People who are very ill, such as people in hospitals or nursing facilities
• Older people in nursing homes

Crusted scabies, also called Norwegian scabies, tends to make skin crusty and scaly, and affects large areas of the body. It’s very contagious and can be hard to treat.

Normally, someone with scabies has about 10 to 15 mites. In contrast, someone with crusted scabies may be infested with millions of mites.

Prevention

To prevent re-infestation and to prevent the mites from spreading to other people, take these steps:

• Clean all clothes and linen. Use hot, soapy water to wash all clothing, towels and bedding used within three days before beginning treatment. Dry with high heat. Dry-clean items you can’t wash at home.
• Starve the mites. Consider placing items you can’t wash in a sealed plastic bag and leaving it in an out-of-the-way place, such as in your garage, for a couple of weeks. Mites die after a few days without food.

Diagnosis

To diagnose scabies, your doctor examines your skin, looking for signs of mites, including the characteristic burrows. When your doctor locates a mite burrow, he or she may take a scraping from that area of your skin to examine under a microscope. The microscopic examination can determine the presence of mites or their eggs.

Treatment

Scabies treatment involves eliminating the infestation with medications. Several creams and lotions are available with a doctor’s prescription.

Your doctor will likely ask you to apply the medication to your whole body, from the neck down, and leave the medication on for at least eight to 10 hours. Some treatments require a second application, and treatments need to be repeated if new burrows and a rash appear.

Because scabies spreads so easily, your doctor will likely recommend treatment for all household members and other close contacts, even if they show no signs of scabies infestation.

Medications commonly prescribed for scabies include:

• Permethrin cream . Permethrin is a topical cream that contains chemicals that kill scabies mites and their eggs. It is generally considered safe for adults, pregnant women, and children ages 2 months and older.
• Lindane lotion. This medication — also a chemical treatment — is recommended only for people who can’t tolerate other approved treatments or for whom other treatments didn’t work. This medication isn’t safe for children younger than age 10 years, women who are pregnant or nursing, or anyone who weighs less than 110 pounds (50 kilograms).
• Crotamiton . This medication is available as a cream or a lotion. It’s applied once a day for two days. The safety of this medication hasn’t been established in children, adults 65 and older, or women who are pregnant or nursing. Frequent treatment failure has been reported with crotamiton.
• Ivermectin. Doctors may prescribe this oral medication for people with altered immune systems, for people who have crusted scabies, or for people who don’t respond to the prescription lotions and creams. Ivermectin isn’t recommended for women who are pregnant or nursing, or for children who weigh less than 33 pounds (15 kilograms).

Although these medications kill the mites promptly, you may find that the itching doesn’t stop entirely for several weeks.