Atopic dermatitis is often simply called eczema because it is the most common type of eczema. “Atopic” refers to a tendency toward allergies, although atopic dermatitis also can be caused by nonallergic reactions. It is characterized by dry, itchy skin and red rashes *
Atopic dermatitis is often caused by a combination of factors including genetic predisposition, dry skin, bacteria, environmental conditions, and/or immune-system dysfunction. It has a strong genetic component and is much more common in people with a personal or family history of eczema, allergies, or asthma * . Atopic dermatitis is often the first symptom of an allergic cascade: it may be followed by the sequential development of food allergies, hay fever * , and asthma. Up to 30 percent of people with atopic dermatitis will develop food allergies, and up to 60 percent will develop hay fever and/or asthma. People with atopic dermatitis are also at increased risk for other inflammatory conditions, such as rheumatoid arthritis and inflammatory bowel disease, and for mental health disorders such as attention deficit hyperactivity disorder (ADHD) and depression. People with celiac disease (gluten intolerance) are three times more likely to have eczema than those without.
Variations in several different genes appear to be involved in atopic dermatitis. In particular, 20 to 30 percent of people with atopic dermatitis have gene mutations that interfere with the production of a protein called filaggrin, which is important both for creating a barrier in the outermost layer of skin that keeps out water and foreign substances and also for producing a natural skin moisturizer.
Contact dermatitis can be caused by many different substances. Workers in contact with certain metals, solvents, or cleaning products are at risk. Healthcare workers are at risk for contact eczema on the hands from latex gloves. Burns, including sunburn, are also risk factors. Poison ivy, poison oak, and poison sumac are the most common causes of allergic contact dermatitis, but allergic contact dermatitis can also be caused by flowers, herbs, and vegetables. Other common causes of contact dermatitis include:
- Nickel in jewelry
- Soaps and detergents
- Chemicals in cleaning products, cosmetics, and perfumes
- Preservatives in creams and lotions
- Chlorine
- Fabric softeners
- Glues for artificial fingernails
- Topical medications
Seborrheic dermatitis is a common inflammatory condition that affects areas of the skin that have many large sebaceous (oil) glands, especially the scalp, face, chest, armpits, and groin. It often occurs seasonally. Genetic predisposition is a major risk factor for seborrheic dermatitis. Other risk factors include:
- Oily skin
- Increased oil production during puberty or pregnancy
- Use of drying lotions that contain alcohol
- Alcohol consumption
- High-fat diets
- Infrequent shampooing
- Stress
- Fatigue
- Hot and humid or cold and dry weather
- Yeast of the genus Malassezia, which are normally present in hair follicles
- Other skin disorders such as acne, rosacea, or psoriasis
*
Dandruff (pityriasis capitis) on the scalps of adolescents and adults and cradle cap on infants' scalps are mild forms of seborrheic dermatitis. Although scalp skin cells constantly die and flake off, dandruff is an overly rapid shedding of the skin that is believed to be caused by an immune-system overreaction to Malassezia yeast that feed on oils in the hair and scalp. Dandruff is not usually a sign of a health problem, but very severe dandruff can be a sign of an immune-system problem.
How Common Is Dermatitis?
Dermatitis is very common. Atopic dermatitis affects 15 to 30 percent of children and 2 to 10 percent of adults. It almost always begins before age five. Over the past few decades, atopic eczema has become two to three times more common in industrialized countries, especially in dry climates and among city dwellers. Although it often improves or disappears in children, their skin may remain dry and easily irritated into adulthood, and an estimated 17 million adult Americans have severe chronic atopic dermatitis.
Contact dermatitis is the most common skin condition requiring medical attention and the most common work-related medical condition. In the United States, it is one of the top 10 reasons for visits to primary-care physicians and accounts for 7 percent of all visits to dermatologists. Contact dermatitis is more common in adults than in children and is twice as common in females as in males. It is more common in Caucasians than in Africans, Asians, or Native Americans.
About 20 percent of American children develop allergic contact dermatitis at some point prior to adolescence, and it is the most common skin condition in children under 11. Poison ivy, poison oak, and poison sumac are the most common allergies in the United States, affecting 50 percent of the population. Allergic contact dermatitis from poison ivy or poison oak afliicts 10 to 50 million Americans of all ages every year. Allergic contact dermatitis from latex affects 1 to 6 percent of the population. Dermatitis is also the most common allergic drug reaction.
Seborrheic dermatitis, including common dandruff, is most common in infants under three months and in adults aged 30 to 60 years. It affects more adult men than women. Dandruff affects 15 to 20 percent of people at some point in their lives. Cradle cap is very common among newborns of all races and both genders, usually appearing in the first six weeks of life and only rarely after 9 to 12 months.
Is Dermatitis Contagious?
Dermatitis is not contagious. However, it is possible to transmit poison ivy between people.
How Do People Know They Have Dermatitis?
In general, dermatitis causes rashes and dry, itchy skin, especially on the face, hands, feet, insides of the elbows, and behind the knees. Scratching can cause the skin to redden, swell, and itch more. The skin may also blister, ooze, crust, or flake off. Different types of dermatitis may look slightly different or are more likely to occur on different parts of the body.
Atopic dermatitis or eczema generally causes dry, itchy skin and rashes that tend to occur in flare-ups followed by periods of improvement. The rashes can occur anywhere on the skin, but they tend to affect different areas at different ages: the face, scalp, hands, and feet of infants; the insides of the elbows and knees and front of the neck in children; and the wrists, ankles, eyelids, and insides of the elbows and knees of adolescents and adults. Scratching the rash can cause redness, swelling, cracking, leaking of clear fluid, crusting, scaling, and thickened skin.
Contact dermatitis causes red, swollen, scaly, and sometimes blistered skin on areas that have contacted the allergen or irritant, usually within 48 hours of exposure. The rashes may itch, sting, or burn.
Seborrheic dermatitis causes patches of red, itchy skin covered by dry, greasy scales that are white, gray, or yellowish, especially on oily areas such as the scalp, face, upper chest, and back. Seborrheic dermatitis can be a long-term condition with periods of improvement followed by flare-ups. Cradle cap and dandruff are fine white scales without redness, inflammation, or itching. However, seborrheic dermatitis in the diaper area of infants is often accompanied by a yeast infection that can cause an itchy rash.
How Do Doctors Diagnose and Treat Dermatitis?
DiagnosisTreatment * (OTC) unscented moisturizers (emollients) immediately after showering or bathing to retain moisture in the skin, and very small amounts of a topical prescription corticosteroid * . For infant eczema, recommendations include “soaking and sealing”—applying a thick layer of cream or ointment directly after a bath without drying the skin first—as well as avoiding irritating fabrics and cleansers. However, different treatments work for different people and conditions, so it may be necessary to try a variety of products to find one that is effective.Dermatitis is usually diagnosed by the appearance of the rash and its location(s). Patients will be questioned about recent contact with potential irritants or allergens, personal and family allergies or asthma, medications, and foods that appear to cause flare-ups. A small piece of affected skin may be removed and examined under a microscope. Eliminating a suspected substance until the dermatitis has cleared up and then reintroducing the substance can be used to identify allergens. In particular, eliminating potential food allergens, such as dairy products, eggs, or nuts, from the diet one at a time can help identify the culprit. Patch tests, in which small amounts of suspected allergens are dabbed, scratched, or pricked into the skin, also are used to identify allergens. Rarely, a skin biopsy is performed to rule out other skin conditions. However, dermatitis—especially seborrheic dermatitis—can be difficult to distinguish from psoriasis. In children who are unlikely to have either cradle cap or dandruff, a sample may be cultured to identify a yeast or other responsible microorganism.