Imagine your hands, face, neck or arms itching relentlessly for hours, plunging you into uncontrollable scratching frenzies that leave your skin wounded and bloody but bring only momentary relief.

That's what more than 15 million adults and children in the United States endure. They have eczema, a noncontagious, chronic disease that begins as a crusted, itchy rash but can eventually make the skin look like a battleground.

The rash and itching can occur anywhere, but they often are found on the backs of the knees, insides of elbows or wrists and the hands. Itching often disrupts sleep and can keep families with afflicted children up all night. Sores caused by the scratching can be vulnerable to bacterial infections.

Eczema can happen any time, but this is a tough season for people with the disease. The cold and dryness of late fall and winter and the forced-air heating used in many homes often make the skin lose moisture, which can spawn eczema problems.

The skin irritations are treated with a variety of remedies, from over-the-counter creams and ointments to powerful prescription antihistamines, steroids and antibiotics. Researchers are also exploring a new drug treatment: A compound developed to help transplant patients stop the body's rejection of foreign tissue is now being tested as a skin ointment to fight eczema. The drug, called tacrolimus, was recently submitted to the Food and Drug Administration for approval for use in eczema patients.

Eczema, also called atopic dermatitis, affects about 10 percent of infants in the United States, according to the National Eczema Association for Science and Education and the American Academy of Dermatology.

About 40 percent of those children outgrow it between ages 5 and 15, but for the rest it's a lifelong struggle.

For other people, symptoms do not appear until adulthood.

Researchers are studying the body's immune system in hopes of finding the cause of the disease and effective treatments. They know patients frequently come from families that have long histories of allergies, which are also caused by a strong reaction of the immune system.

Eczema can sometimes be triggered by an allergic reaction, but for other people there is no known cause.

In eczema sufferers, the "immune cells are eager to overreact to trivial things," says Guy Webster, dermatologist and vice chairman of the department of dermatology at Thomas Jefferson Medical College in Philadelphia. "It's like a man with a bad temper. Stuff that others would ignore, he takes great offense to. The skin is just irritable; little things make it go nuts."

Frequent irritants include wool or synthetic fibers, soaps, stress and sweating.

Treatment varies depending on the severity of the symptoms. Doctors first counsel patients to keep their skin hydrated through a daily moisturizing routine, which protects it from the drying and cracking that can lead to eczema problems. Patients are often told to take short showers and pat their skin dry rather than rubbing it with a towel. They should also apply creams and moisturizers on the skin while it is still wet after a shower to help seal in the moisture, says Jon Hanifin, a professor of dermatology at Oregon Health Sciences University in Portland. "When the skin dries out, it's like the mud flats in a river. The cells on the surface of the skin pull apart and you get microscopic cracks. That's when the itching and irritation starts."

Finding an effective treatment can be perplexing.

"No medicine is great for everybody. Everyone has his own recipe. I work with each patient as an individual to find the best treatment," says Roselyn E. Epps, a pediatric dermatologist at Children's National Medical Center in Washington.

Doctors often prescribe topical steroids, which range from over-the-counter hydrocortisone creams to more potent prescription drugs. "They only hold back the tide, they don't ever cure it," Hanifin says. In addition, the most powerful of these steroid creams can have serious side effects.

"If you use topical steroids every day for more than a month, you get thinning of the skin," Hanifin says. "Mainly the second layer of the skin weakens and blood vessels show through the skin and it's easily bruised, which looks nasty."

Thinned skin can also be more vulnerable to eczema and can cause a vicious cycle of treatment and outbreaks, says Webster.

To cut down on the use of topical steroids, Hanifin prescribes a medium-strength topical steroid twice a day for a week to calm the itching. Once the skin starts to heal, patients use it every second or third day for the next two weeks. "The majority are holding quite well on the twice-a-week treatment," he says.

"Often pediatricians are too conservative and don't use adequate-strength topical steroids," Hanifin says.

While topical steroids work for many patients, others need more powerful drugs, such as steroids taken orally or injected. These potent drugs can have severe effects, from stunting growth to causing cataracts and osteoporosis.

"You have to be very careful about the effects of too long an exposure to any one drug," says Alan Moshell, branch chief of the National Institute of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health. "You have to weigh the risks and the benefits. That's the art of dermatology in dealing with a disease where the drugs have significant side effects."

Doctors also prescribe antihistamines to some patients to help quell the itchiness.

Antoine Jenkins, 36, of Manassas, knows about treatments and their potential dangers. He's had eczema since infancy.

The itching is relentless, says Jenkins. "You scratch and scratch, but the itching never goes away."

It's worse at night. Jenkins takes an antihistamine to help stop the itching so he can sleep, but sometimes the drug keeps him awake. He's scratched his skin until he bleeds. "It may stop the itching for a minute, but during the healing process, when you get a scab, it will start itching again," he says.

He also taken a number of drugs, including prednisone, a systemic steroid, and liquid cyclosporin, a foul-tasting immune suppressant.

Even worse than his skin are his eyes. They itch on the outside and the inside of his eyelids.

His eyes redden, swell and produce mucus, says John Gottsch, an ophthalmologist at Johns Hopkins's Wilmer Eye Institute in Baltimore, who treats Jenkins.

"You can imagine the intensity of the itching," Gottsch says. This eye problem is commonly treated with antihistamines and topical steroids, but the steroids can increase pressure in the eyes and cause cataracts.

In June, Gottsch prescribed cyclosporin eye drops four times a day to stop the itching, but Jenkins used them only at night because the thick drops stung his eyes. Although they provide relief, "it takes a while to be able to see out of my eyes," Jenkins says.

Doctors at Hopkins plan a study of another type of cyclosporin eye drops made by Allergan Inc. to see if they are less irritating. While the study will start soon, three clinical trials have been completed on the ointment form of tacrolimus for the skin.

In all the trials, patients' skin improved after use, says Ira Lawrence, vice president of research and development for Fujisawa Healthcare Inc., which plans to market the drug as Protopic.