Atopic dermatitis (AD is a type of eczema) is an inflammatory, chronically relapsing, non-contagious and a pruritic disease of unknown origin that usually starts in early infancy. Atopic dermatitis is a very common, often chronic (long-lasting) skin disease that affects a large percentage of the world's population. It is also called eczema, dermatitis, or atopy. Most commonly, it may be thought of as a type of skin allergy or sensitivity. The atopic dermatitis triad includes asthma, allergies (hay fever), and eczema. There is a known hereditary component of the disease, and it is seen more in some families. The hallmarks of the disease include skin rashes and itching.

The word "dermatitis" means inflammation of the skin. "Atopic" refers to diseases that are hereditary, tend to run in families, and often occur together. In atopic dermatitis, the skin becomes extremely itchy and inflamed, causing redness, swelling, cracking, weeping, crusting, and scaling. Dry skin is a very common complaint and an underlying cause of some of the typical rash symptoms.
The skin of a patient with atopic dermatitis reacts abnormally and easily to irritants, food, and environmental allergens and becomes red, flaky and very itchy. It also becomes vulnerable to surface infections caused by bacteria. The skin on the flexural surfaces of the joints (for example inner sides of elbows and knees) are the most commonly affected regions in people. Atopic dermatitis often occurs together with other atopic diseases like hay fever, asthma and conjunctivitis. It is a familial and chronic disease and its symptoms can increase or disappear over time. Atopic dermatitis in older children and adults is often confused with psoriasis. Atopic dermatitis afflicts humans, particularly young children; it is also a well-characterized disease in domestic dogs.

Eczema is used as a general term for many types of skin inflammation (dermatitis) and allergic-type skin rashes. There are different types of eczema, like allergic, contact, irritant, and nummular eczema. Several other forms have very similar symptoms. Atopic dermatitis is typically a more specific set of three associated conditions occurring in the same person including eczema, allergies, and asthma. Not every component has to be present at the same time, but usually these patients are prone to all of these three related conditions.

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. 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.

• Genetics: A family history of atopic dermatitis is common.
• Infection: The skin of patients with atopic dermatitis is colonized by S aureus. Clinical infection with S aureus often causes a flare of atopic dermatitis, and S aureus has been proposed as a cause of atopic dermatitis by acting as a superantigen.
• Hygiene: The hygiene hypothesis is touted as a cause for the increase in atopic dermatitis. This attributes the rise in atopic dermatitis to reduced exposure to various childhood infections and bacterial endotoxins.
• Climate: Atopic dermatitis flares occur in extremes of climate.
• Food antigens: The role of food antigens in the pathogenesis of atopic dermatitis is controversial, both in the prevention of atopic dermatitis and by the withdrawal of foods in persons with established atopic dermatitis.
• Probiotics: The role of probiotics in the diet of patients with atopic dermatitis remains controversial
• Aeroallergens: A role for aeroallergens and house dust mites has been proposed, but this awaits further corroboration.
• Stress: It is not a primary cause but can lead to exacerbation of the disease

• Approximately 50% of the patients who develop the condition display symptoms before the age of 1, and 80% display symptoms within the first 5 years of life.
• Symptoms may vary from person to person but they are usually present as a red, inflamed, and itchy rash and can quickly develop into raised and painful bumps. The first sign of atopic dermatitis is the red to brownish-gray colored patches that are usually very itchy. Itching may become more intense during the night. The skin may present small and raised bumps which may be crusting or oozing if scratched, which will also worsen the itch. The skin tends to be more sensitive and may thicken, crack or scale.
• When appearing in the area next to the eyes, scratching can cause redness and swelling around them and sometimes, rubbing or scratching in this area causes patchy loss of eyebrow hair and eyelashes.
• The symptoms of atopic dermatitis vary with the age of the patients. Usually, in infants, the condition causes red, scaly, oozy and crusty cheeks and the symptoms may also appear on their legs, neck and arms. Symptoms clear in about half of these children by the time they are 2 or 3 years old. In older children, the symptoms include dry and thick, scaly skin with a very persistent itch, which is more severe than in infants. Adolescents are more likely to develop thick, leathery and dull-looking lesions on their face, neck, hands, feet, fingers or toes.
• How atopic dermatitis affects the skin can be changed by patterns of scratching and resulting skin infections. Some people with the disease develop red, scaling skin where the immune system in the skin becomes very activated. Others develop thick and leathery skin as a result of constant scratching and rubbing. This condition is called lichenification. Still others develop papules, or small raised bumps, on their skin. When the papules are scratched, they may open (excoriations) and become crusty and infected.

Is atopic dermatitis contagious?
No. Atopic dermatitis itself is definitely not contagious and it cannot be passed from one person to another through skin contact. There is generally no cause for concern in being around someone with even an active case of atopic dermatitis, unless they have active skin infections.

Atopic Dermatitis At A Glance

• Atopic dermatitis is a type of eczema.
• The skin sensitivity of this disease may be inherited and genetically determined.
• The patient's skin may be "super sensitive" to many irritants.
• Dry scaly patches develop in a characteristic distribution.
• Itching varies but may be intense and scratching hard to resist.
• Scratching can cause skin thickening and darkening and lead to further complications, including bacterial infection.
• Extremely dry skin can break down and ooze or weep.
• If the itch can be controlled, the rash (which is aggravated by vigorous scratching) may be more readily contained.