Atopic dermatitis is thought to affect about 10-15% of the population, and is more common in cooler climates and urban areas. It usually starts during the first year of life or in early childhood – most often in infants between 2 and 6 month of age. Half of all diagnoses are made during the first year of life. An additional 30% begin between 1 and 5 years of age.
The prospects for people with atopic dermatitis are generally good. Most cases resolve completely by early adulthood, or even sooner. However, it will persist in 2-10% of adults, when it occurs more often as mild to moderately severe hand dermatitis.
The disease has a fluctuating course, as we have described, flaring up rapidly and disappearing just as quickly, without any visible or identifiable trigger. Sometimes, however, patients can attribute the flare to a recent activity or event. For example, eating seafood or egg protein is blamed, or using a particular soap or bath product. One must be aware that such associations are often coincidental and, in reality, the disease follows its own “natural” course. The duration of remissions, or eczema-free periods, between flares is extremely variable, lasting from a few months to several years.
One can’t predict with any certainly which cases will disappear completely, and when this may happen. They are, however, some risk factors for persistence of atopic dermatitis into adulthood. These include: being female, onset after age 2, severe dermatitis in childhood, a family history of atopy, and previous or existing asthma or allergic rhinitis.
Allergic contact dermatitis
This is seen in about 1-2 % of Western societies; it’s more common in people who have used medical applications to the skin for chronic skin diseases. It develops differently from atopic dermatitis. As the name implies, the condition is caused by direct contact with a ‘trigger agent’, or allergen, and one can expect the symptoms to disappear if this substance is kept from reaching the skin.
Allergic contact dermatitis can occur early in life, most often seen the first time with adhesive plasters (‘Band-Aids’). Or a girl may discover she has a nickel allergy at the time of puberty when she starts to wear jewelry.
Symptoms of allergic contact dermatitis may often be avoided with a little care, by keeping away from contact with known substances that provoke the allergy. Although this seems very easy, it is not always possible to identify an individual’s particular trigger agent. This may be partly because the body requires time to develop it’s ‘protective’ allergic reaction. Delay between exposure and the appearance of symptoms can blur the connection.
In some cases, the allergen is known but cannot be avoided, because it’s part of the environment — for instance, sunlight, or something in the workplace. In rare instances, the allergen may cause quite severe allergic reactions, such as those seen with antibiotics.
Irritant contact dermatitis
This condition affects near 3% of the population, and is more frequent in adults. Patients with atopic dermatitis are especially prone to this type of irritant effect. People may develop reactions to products that come into contact with the skin even if they have been using them for many years without problems. This is because it takes repeated injury to the skin over time for the reaction to develop.
Typically these irritant substances are clothing or chemicals. Once a person is affected, the typical skin reaction will usually appear within 6-12 hours of further contact, at the site where the irritant has contacted the skin. The dermatitis disappears rapidly if there is no further contact with the irritant, provided there is no infection present. Repeated exposure to an irritant at the workplace is sometimes difficult to avoid and requires special measures.