Atopic dermatitis (eczema) is an itchy inflammation of your skin. It's a long-lasting (chronic) condition that may be accompanied by asthma or hay fever. Eczema is most often seen in infants and children, but it can continue into adulthood or first appear later in life.
Eczema may affect any area, but it classically appears on your arms and behind the knees. It tends to flare periodically and then subside. The cause of atopic dermatitis, or eczema, is unknown, but it may result from a malfunction in the body's immune system.
Self-care measures, such as avoiding soaps or other irritants and applying creams or ointments, can help relieve itching. See your doctor if your symptoms distract you from your daily routines or prevent you from sleeping.

Causes

What causes atopic dermatitis?

The cause of atopic dermatitis is not known, but the disease seems to result from a combination of genetic (hereditary) and environmental factors. There seems to be a basic hypersensitivity and an increased tendency toward itching. Evidence suggests that the disease is associated with other so-called atopic disorders such as hay fever (seasonal allergies) and asthma, which many people with atopic dermatitis also have. In addition, many children who outgrow the symptoms of atopic dermatitis go on to develop hay fever or asthma. Although one disorder does not necessarily cause another, they may be related, thereby giving researchers clues to understanding atopic dermatitis.
While emotional factors and stress may in some cases exacerbate or initiate the condition, they do not seem to be a primary or underlying cause for the disorder. In the past, there was some thought that perhaps atopic dermatitis was entirely caused by an emotional disorder.


Signs and symptoms of atopic dermatitis (eczema) include:

• Red to brownish-gray colored patches
• Itching, which may be severe, especially at night
• Small, raised bumps, which may leak fluid and crust over when scratched
• Thickened, cracked or scaly skin
• Raw, sensitive skin from scratching

Though the patches can occur anywhere, they most often appear on the hands and feet, in the front of the bend of the elbow, behind the knees, and on the ankles, wrists, face, neck and upper chest. Atopic dermatitis can also affect the skin around your eyes, including your eyelids. Scratching can cause redness and swelling around the eyes. Sometimes, rubbing or scratching in this area causes patchy loss of eyebrow hair and eyelashes.
Atopic dermatitis most often begins in childhood before age 5 and may persist into adulthood. For some, it flares periodically and then subsides for a time, even up to several years. Itching may be severe, and scratching the rash can make it even itchier. Breaking this itch-scratch cycle can be challenging.
Factors that worsen atopic dermatitis
Most people with atopic dermatitis also have Staphylococcus aureus bacteria growing on their skin. The staph bacteria multiply and can worsen symptoms, increasing the severity of the disease.
Other factors that can worsen signs and symptoms of atopic dermatitis include:

• Long, hot baths or showers
• Dry skin
• Stress
• Sweating
• Rapid changes in temperature
• Low humidity
• Solvents, cleaners, soaps or detergents
• Wool or man-made fabrics or clothing
• Dust or sand
• Cigarette smoke
• Certain foods, such as eggs, milk, fish, soy or wheat

Infantile eczema
When atopic dermatitis occurs in infants, it's called infantile eczema. This condition may continue into childhood and adolescence.
Infantile eczema often involves an oozing, crusting rash, mainly on the face and scalp, but it can occur anywhere. After infancy, the rash becomes dryer and tends to be red to brown-gray in color. In adolescence, the skin may be scaly or thickened and easily irritated. The intense itching may continue.

How is atopic dermatitis diagnosed?

Atopic dermatitis is generally easily diagnosed based on a physical exam and visual inspection of the skin by a physician or dermatologist. Additionally, the history given by the patient and contributory family history help to support the diagnosis. A physician may ask about any history of similar rashes and other medical problems including hay fever (allergies) and asthma. While currently there may be no single specific laboratory test that says unequivocally "this is atopic dermatitis," a skin biopsy (a sample of a small piece of skin that is sent to the lab for examination under the microscope) may be helpful to establish the diagnosis in harder cases. Additionally, gentle skin swabs (long cotton tip applicator or Q-tip) samples may be sent to the lab to exclude infections of the skin which may mimic atopic dermatitis.
Since itching tends to be the main common symptom of the disease for many patients, it is not possible to say all itching is atopic dermatitis. Itching may be seen in many other medical conditions that have nothing to do with eczema. Each patient experiences a unique combination of symptoms, and the symptoms and severity of the disease may vary over time. The doctor bases the diagnosis on the individual's symptoms and may need to see the patient several times to make an accurate diagnosis. It is important for the doctor to rule out other diseases and conditions that might cause skin irritation. In some cases, the family doctor or pediatrician may refer the patient to a dermatologist or allergist (allergy specialist) for further evaluation.
A valuable diagnostic tool is a thorough medical history, which provides important clues as to the possible causes of the patient's ailment. The doctor may ask about all of the following: a family history of allergic disease, whether the patient also has diseases such as hay fever or asthma, exposure to irritants, sleep disturbances, any foods that seem to be related to skin flares, previous treatments for skin-related symptoms, use of steroids, and the effects of symptoms on schoolwork, career, or social life. Sometimes, it is necessary to do a biopsy of the skin or patch testing to determine if the skin's immune system overreacts to certain chemicals or preservatives in skin creams. A preliminary diagnosis of atopic dermatitis can be made if the patient has three or more characteristics from each of two categories: major features and minor features. Some of these characteristics are listed in the box below.
Skin scratch/prick tests (which involve scratching or pricking the skin with a needle that contains a small amount of a suspected allergen) and blood tests for airborne allergens generally are not as useful in diagnosing atopic dermatitis as a medical history and careful observation of symptoms. However, they may occasionally help the doctor rule out or confirm a specific allergen that might be considered important in the diagnosis. Negative results on skin tests are reliable and may help rule out the possibility that certain substances are causing skin inflammation in the patient. However, positive skin scratch/prick test results are difficult to interpret in people with atopic dermatitis and are often inaccurate. In some cases, where the type of dermatitis is unclear, blood tests to check the level of eosinophils (a type of white blood cell) or IgE (an antibody whose levels are often high in atopic dermatitis) are helpful.

What are the stages of atopic dermatitis?

Atopic dermatitis affects each child differently, both in terms of onset and severity of symptoms. In infants, atopic dermatitis typically begins around 6 to 12 weeks of age. It may first appear around the cheeks and chin as a patchy facial rash, which can progress to red, scaling, oozing skin. The skin may become infected. Once the infant becomes more mobile and begins crawling, exposed areas such as the knees and elbows may also be affected. An infant with atopic dermatitis may be restless and irritable because of the itching and discomfort. Many infants improve by 18 months of age, although they remain at greater than normal risk for dry skin or hand eczema later in life.
In childhood, the rash tends to occur behind the knees and inside the elbows, on the sides of the neck, and on the wrists, ankles, and hands. Often, the rash begins with papules that become hard and scaly when scratched. The skin around the lips may be inflamed, and constant licking of the area may lead to small, painful cracks. Severe cases of atopic dermatitis may affect growth, and the child may be shorter than average.
The disease may go into remission (disease-free period). The length of a remission varies, and it may last months or even years. In some children, the disease gets better for a long time only to come back at the onset of puberty when hormones, stress, and the use of irritating skin-care products or cosmetics may cause the condition to flare.
Although a number of people who developed atopic dermatitis as children also experience symptoms as adults, it is less common (but possible) for the disease to show up first in adulthood. The pattern in adults is similar to that seen in children; that is, the disease may be widespread or limited. In some adults, only the hands or feet may be affected and become dry, itchy, red, and cracked. Sleep patterns and work performance may be affected, and long-term use of medications to treat the condition may cause complications. Adults with atopic dermatitis also have a predisposition toward irritant contact dermatitis, especially if they are in occupations involving frequent hand wetting, hand washing, or exposure to chemicals. Some people develop a rash around their nipples. These localized symptoms are difficult to treat, and people often do not tell their doctor because of modesty or embarrassment. Adults may also develop cataracts that are difficult to detect because they cause no symptoms. Therefore, the doctor may recommend regular eye exams.

Treatments for atopic dermatitis (eczema) aim to reduce inflammation, relieve itching and prevent future flare-ups. Over-the-counter (nonprescription) anti-itch creams, along with other self-care measures, may help control mild atopic dermatitis.
Although atopic dermatitis is related to allergies, eliminating allergens is rarely helpful in clearing the condition. Occasionally, items that trap dust — such as feather pillows, down comforters, mattresses, carpeting and drapes — can worsen the condition. Allergy shots usually aren't successful in treating atopic dermatitis and might even make the condition worse.
Medications

• Corticosteroid creams or ointments. Your doctor may recommend prescription corticosteroid creams or ointments to ease scaling and relieve itching. Some low-potency corticosteroid creams are available without a prescription, but you should always talk to your doctor before using any topical corticosteroid. Side effects of long-term or repeated use can include skin irritation or discoloration, thinning of the skin, infections, and stretch marks on the skin.
• Antibiotics. You may need antibiotics if you have a bacterial skin infection or an open sore or fissure caused by scratching. Your doctor may recommend taking antibiotics for a short time to treat an infection or for longer periods of time to reduce bacteria on your skin and to prevent recurrent infections.
• Oral antihistamines. If itching is severe, oral antihistamines may help. Diphenhydramine (Benadryl, others) can make you very sleepy and may be helpful at bedtime. If your skin cracks open, your doctor may prescribe mildly astringent wet dressings to prevent infection.
• Oral corticosteroids. For more severe cases, your doctor may prescribe a short-course of oral corticosteroids, such as prednisone, to reduce inflammation and to control symptoms. These medications are effective but can't be used long term because of potential serious side effects, which include cataracts, loss of bone mineral (osteoporosis), muscle weakness, decreased resistance to infection, high blood pressure and thinning of the skin.
• Immunomodulators. A class of medications called immunomodulators, such as tacrolimus (Protopic) and pimecrolimus (Elidel), affects the immune system and may help maintain normal skin texture and reduce flares of atopic dermatitis. This prescription-only medication is approved for children over the age of 2 and for adults. Due to possible concerns about the effect of these medications on the immune system when used for prolonged periods of time, the Food and Drug Administration recommends that Elidel and Protopic be used only when other treatments have failed, or if someone can't tolerate other treatments.

Light therapy (phototherapy)
As the name suggests, this treatment uses natural or artificial light. The simplest and easiest form of phototherapy involves exposing your skin to controlled amounts of natural sunlight. Other forms of light therapy include the use of artificial ultraviolet A (UVA) or ultraviolet B (UVB) light either alone or in combination with medications.
Though effective, long-term light therapy has many harmful effects, including premature skin aging and an increased risk of skin cancer. For these reasons, it's important to consult your doctor before using light exposure as treatment for atopic dermatitis. Your doctor can advise you on possible advantages and disadvantages of light exposure in your specific situation.
Infantile eczema
Treatment for infantile eczema includes identifying and avoiding skin irritations, avoiding extreme temperatures, and using bath oils, lotions, creams or ointments to lubricate your baby's skin.
See your baby's doctor if these measures don't improve the rash or if the rash looks infected. Your baby may need a prescription medication to control the symptoms or to treat the infection. Your doctor may recommend an oral antihistamine to help lessen the itch and to cause drowsiness, which may be helpful for nighttime itching and discomfort

Prevention

Avoiding dry skin may be one factor in helping prevent future bouts of dermatitis. These tips can help you minimize the drying effects of bathing on your skin:

• Bathe less frequently. Most people who are prone to atopic dermatitis don't need to bathe daily. Try going a day or two without a shower or bath. When you do bathe, limit yourself to 15 to 20 minutes, and use warm, rather than hot, water. Using a bath oil also may be helpful.
• Use only certain soaps or synthetic detergents. Choose mild soaps that clean without excessively removing natural oils. Deodorant and antibacterial soaps may be more drying to your skin. Use soap only on your face, underarms, genital areas, hands and feet. Use clear water elsewhere.
• Dry yourself carefully. Brush your skin rapidly with the palms of your hands, or gently pat your skin dry with a soft towel after bathing.
• Moisturize your skin. Moisturizers provide a seal over your skin to keep water from escaping. Thicker moisturizers work best, such as over-the-counter brands Cetaphil, Vanicream and Eucerin. You may also want to use cosmetics that contain moisturizers. If your skin is extremely dry, you may want to apply an oil, such as baby oil, while your skin is still moist. Oil has more staying power than moisturizers do and prevents the evaporation of water from the surface of your skin.

 Refrence:

1. Weston WL, et al. Epidemiology, clinical manifestations, and diagnosis of atopic dermatitis (eczema). http://www.uptodate.com/home/index.html. Accessed May 20, 2009.
2. Weston WL, et al. Treatment of atopic dermatitis (eczema). http://www.uptodate.com/home/index.html. Accessed May 20, 2009.
3. Bieber T. Mechanisms of disease: Atopic dermatitis. New England Journal of Medicine. 2008;358:1483.
4. Eczema/atopic dermatitis. American Academy of Dermatology. http://www.aad.org/public/Publications/pamphlets/EczemaAtopicDermatitis.htm. Accessed May 20, 2009.
5. What is atopic dermatitis? National Institute of Arthritis and Musculoskeletal and Skin Diseases. http://www.niams.nih.gov/hi/topics/dermatitis/ffdermatitis.htm. Accessed May 20, 2009.
6. FDA public health advisory Elidel (pimecrolimus) cream and Protopic (tacrolimus) ointment. U.S. Food and Drug Administration. http://www.fda.gov/cder/drug/advisory/elidel_protopic.htm. Accessed May 20, 2009.