Atopic dermatitis (AD), also known as atopic eczema, is a type of inflammation of the skin (dermatitis). It results in itchy, red, swollen, and cracked skin. Clear fluid may come from the affected areas which often become thickened over time.[1] It typically starts in childhood with changing severity over the years.[1][2] In children under one year of age much of the body may be affected. As they get older the back of the knees and front of the elbows are the most common area for the rash. In adults the hands and feet are most affected.[2] Scratching worsens symptoms and affected people have an increased risk of skin infections. Many people with atopic dermatitis develop hay fever or asthma.[1]

The cause is not known but believed to involve genetics, immune system dysfunction, environmental exposures, and difficulties with the permeability of the skin.[1][2] If one identical twin is affected there is an 85% chance the other will also have the condition.[3] Those who live in cities and dry climates are more commonly affected. Exposure to chemicals or frequent hand washing makes symptoms worse. While emotional stress may make the symptoms worse it is not a cause. The disorder is not contagious.[1] The diagnosis is typically based on the signs and symptoms. Other diseases that need to be excluded before making a diagnosis include contact dermatitis, psoriasis, and seborrheic dermatitis.[2]

Treatment involves avoiding things that make it worse, daily bathing with application of a moisturising cream afterwards, applying steroid creams when flares occur, and medications to help with itchiness.[2] Things that commonly make it worse include wool clothing, soaps, perfumes, chlorine, dust, and cigarette smoke. Phototherapy may be useful in some people. Steroid pills may occasionally be used if other measures are not effective.[1] Antibiotics (either by mouth or topically) may be needed if a bacterial infection develop.[2] Dietary changes are only needed if food allergies are suspected.[1]

Atopic dermatitis affects about 20% of people at some point in their lives.[1][4] It is more common in younger children.[2] Males and females are equally affected.[1] Many people outgrow the condition.[2] Atopic dermatitis is sometimes called eczema, a term that also refers to a larger group of skin conditions.[1] Other names include "infantile eczema", "flexural eczema", "prurigo Besnier", "allergic eczema", and "neurodermatitis".[5]

People with AD often have dry and scaly skin that spans the entire body, except perhaps the diaper area, and intensely itchy red, splotchy, raised lesions to form in the bends of the arms or legs, face, and neck.[6][7][8][9][10] These lesions then weep, crack, swell, and crust over.[10] These lesions are at a heightened risk for bacterial, fungal, or viral colonisation.[10]

The cause of AD is not known, although there is some evidence of genetic factors, and some evidence that growing up in a sanitary environment encourages AD.[7]

It seems to have a genetic component. Many people with AD have a family history of atopy. Atopy is an immediate-onset allergic reaction such as asthma, food allergies, AD or hay fever.[6][7] In 2006 it was discovered that mutations in the gene for the production of filaggrin strongly increased the risk for developing atopic dermatitis. Most importantly two mutations were found that affect approximately 5% of people in Western Europe that may disrupt the production of filaggrin. Filaggrin is a protein that plays an important role in the retention of water in the stratum corneum. People who have these mutations often have dry skin.[11] Filaggrin also plays an important role in keeping the skin surface slightly acidic, hence giving it anti-microbial effects. It is broken down into trans-urocanic acid which keeps the pH low.[12]

According to the hygiene hypothesis, when children are brought up exposed to allergens in the environment at a young age, their immune system is more likely to tolerate them, while children brought up in a modern "sanitary" environment are less likely to be exposed to those allergens at a young age, and, when they are finally exposed, develop allergies. There is some support for this hypothesis with respect to AD.

Those exposed to dogs while growing up have a lower risk of atopic dermatitis.[13] There is also support from epidemiological studies for a protective role for helminths against AD.[14] Likewise children with poor hygiene are at a lower risk for developing AD, as are children who drink unpasteurised milk.[14] Exposure to dust mites is believed to contribute to one's risk of developing AD.[15]

A diet high in fruits seems to have a protective effect against AD, whereas the opposite seems to be true for fast foods.[14]

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Atopic dermatitis - Wikipedia, the free encyclopedia