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Scabies is an itchy skin condition caused by a tiny, eight-legged burrowing mite called Sarcoptes scabiei. The presence of the mite leads to intense itching in the area of its burrows. The sheer discomfort of scabies can produce an almost irresistible urge to scratch, especially while you're in bed at night.

Scabies is contagious and can spread quickly through close physical contact in a family, child-care group, school class or nursing home. Because of the contagious nature of scabies, doctors often recommend treatment for entire families or contact groups to eliminate the mite.

Medications applied to your skin kill the mites, although you may still experience some itching for several weeks.

Signs and symptoms of scabies include:

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

The pencil-like marks or tracks typically appear in folds of your skin. Though almost any part of your body may be involved, scabies is most often found:

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

The mite that causes scabies in humans is microscopic and almost impossible to see without a magnifying glass. The female mite burrows just beneath your skin and produces a tunnel in which it deposits eggs. The eggs mature in 21 days, and the new mites 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, sharing clothing or bedding with an infected person can spread the mites.

Dogs, cats and humans all are affected by their own distinct species of mite. Each species of mite prefers one specific type of host and doesn't live long away from that preferred host. So 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.

Bathing and over-the-counter preparations won't eliminate scabies. Talk to your doctor if you have signs and symptoms or if you believe you've had contact with someone who has scabies.

Many skin conditions, such as dermatitis or eczema, are associated with itching and small bumps on the skin. If you have an itchy, irritating skin condition, see your doctor to determine the exact cause, so that you'll receive proper treatment.

Scabies can become a persistent and widespread problem in certain groups of people, including those with altered immune systems, such as people with HIV or chronic leukemia. Scabies can also be a problem for those who are very ill, such as people in hospitals or nursing facilities.

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.

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.

Treatment involves eliminating the scabies infestation with medications. Several creams and lotions are available. You usually apply the medication over all your body, from your neck down, and leave the medication on for at least eight hours. Two medications commonly prescribed are permethrin (Elimite, Acticin) and crotamiton (Eurax). Although these medications kill the mites promptly, you may find that the itching doesn't stop entirely for several weeks.

Doctors sometimes prescribe oral medications for people with altered immune systems or for people who don't respond to the prescription lotions and creams.

Because scabies spreads so easily, your doctor may recommend treatment for all family members and their sexual partners, even if they show no signs of scabies infestation.

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

• Clean all clothes and linen. Use hot, soap water to wash all clothing, towels and bedding you used before 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 if they don't eat for a week.

Itching may persist for some time after you apply medication to kill the mites. These steps may help you find relief from itching:

• Cool and soak your skin. Soaking in cool water or applying a cool, wet washcloth to irritated areas of your skin may minimize itching.
• Apply soothing lotion. Calamine lotion, available without a prescription, can effectively relieve the pain and itching of minor skin irritations.
• Take antihistamines. At your doctor's suggestion, you may find that over-the-counter antihistamines relieve the allergic symptoms caused by scabies.