Atopic dermatitis is diagnosed by the history of the symptoms and the appearance of the rash. There is no test that will diagnose eczema although tests may be done to help identify triggers for the problem.
Unlike many other skin conditions, eczema is not a rash that causes itching. Rather it starts as itchy skin that only forms a rash after the patient scratches at it. This scratching damages the skin and leads to the characteristic appearance of the rash. This is very important since if the itching can be blocked or controlled then the rash will not appear!
The rash itself is not unique to eczema but appears as redness with small bumps or even blisters. The skin may crack and some clear fluid may ooze out of the openings. With chronic scratching the skin may thicken and form leathery patches.
More unique to eczema is the location of the rash. In infants the rash is localized to areas where the child can scratch such as the face, chest and abdomen, arms and legs. Often there is no rash in covered areas such as under the diaper. In older children and adults the rash is classically found in front of the elbows and behind the knees but in more severe cases may be found anywhere within reach of scratching.
There are many triggers for the skin itching that leads to the rash. Irritants such as harsh soaps, chemicals, rough fabrics, heat and sweating are common problems for eczema patients. Avoidance of these irritants through use of gentle soaps, wearing cotton clothing, and keeping cool and dry can help prevent itching.
People with atopic dermatitis are more susceptible to skin infections by various bacterial, fungal and viral infections.
Many patients have large amounts of a common skin bacterium, called Staphylococcus aureus, which can worsen the itching and eczema.
Allergies are also a significant trigger of eczema. Indoor allergens that directly touch the skin, such as pets and dust mites, cause the most problems, although pollens and mold spores in the air can also worsen the condition.
Food allergies are also a major trigger particularly in children. Egg and milk allergy are the most common food allergies in children with worsening eczema, although other food allergies are also common.
Identifying allergic triggers in eczema patients is very important. Allergy testing using a skin test or blood test can be very revealing and avoidance of these triggers, both environmental and food allergens, can significantly improve the problem.
In addition to avoiding any known triggers, the key step in treating eczema is moisturization. Soft, smooth skin tends to itch less and be less irritable than dry skin. Moisturizing every day, especially after bathing, is critical. If eczema still flares up despite moisturization then using an anti-inflammatory cream or ointment such as a topical steroid or calcineurin inhibitor may be used. More advanced measures for severe eczema are available.