Atopic dermatitis (AD) is a chronic, highly itchy skin condition that frequently relapses. It most often begins in childhood, although a small number of people develop the disease as an adult. One of the most noticeable symptoms of AD is the rash or patches of dry, scaly skin.1
Acute lesions of AD are red, have papules (bumps or pimples without pus), leak fluid (weepy) and have scratch marks, breaks in the skin, or appear as the skin has been rubbed raw. Chronic lesions of AD have areas of thickened scaly skin (also called lichenification) and scarred, lumpy skin (also called fibrotic nodules). Chronic lesions and acute lesions may occur in the same areas of skin.1
The rash caused by AD usually appears in a characteristic pattern depending on the age of the person:
- In infants and young children, the rash shows up on the scalp or face, especially the cheeks or chin, and the arms and legs, particularly the outer creases of the elbows and knees in infants and the inner creases of the joints in young children
- In older children, AD frequently appears as a rash on the inside creases of the elbows or knees, the neck, wrists, ankles, and/or the crease between the buttocks and the thighs
- In adults, the rash can appear anywhere, including the inner creases of the elbows or knees, and/or the nape of the neck, or it may be localized to just the hands, feet, or nipples2
How atopic dermatitis causes rash
AD is caused by a combination of genetic, immunologic, and environmental factors. In people with AD, there can sometimes be a decrease or lack of filaggrin in the skin. Filaggrin is a protein that plays a key role in the structure and formation of the outermost corneal layer of the skin. The lack of or decrease in filaggrin has been traced back to genetic mutations in the FLG gene. Not having enough filaggrin in the skin layers leads to a reduced ability to maintain the skin’s natural amount of water. Excess water loss can lead to dry skin, which then causes itchiness. The lack of filaggrin may also allow for the entry of airborne allergens to enter the skin, which could lead to an inflammatory response by the immune system.
Another theory suggests that the normal pH of the skin barrier may be affected by filaggrin defects, which could lead to the overgrowth of bacteria. This could then trigger the immune system to create inflammatory skin lesions. There is also emerging evidence that the dysfunction in the immune system in patients with eczema not only causes disease but also decreases the amount of functional filaggrin. Immune system dysfunction also creates an increase in inflammation in people with AD.3,4
Treating the rash of atopic dermatitis
Moisturizers are one of the basic necessities for people with AD, regardless of the severity of their disease. Some of the anti-inflammatory medications available for treating AD also come in moisturizer formulations, which can help provide additional barrier repair and control itchiness.
Medications used in the treatment of AD include:
- Topical corticosteroids, to reduce redness, inflammation, and itching
- Topical calcineurin inhibitors, to stop the dysfunctional immune response and reduce redness and itching
- Immunomodulators, which also target the dysfunctional immune response to reduce symptoms
- Antibiotics, to fight infection5
Phototherapy, which uses light waves directed at the skin, is a second-line treatment strategy. That is, it is only recommended for use after other treatments and lifestyle approaches have failed to improve symptoms of AD. Phototherapy is sometimes used as a maintenance therapy in people with chronic AD.6
Other symptoms of atopic dermatitis
In addition to the rash, AD can cause itch, weepy sores, bumps or papules, blisters, and a change in skin color. Some people also experience eye symptoms or cracks behind the ears. Over time, the areas of skin affected by AD may become thickened.