The simple definition of dermatitis is inflammation of the skin. Many people think of dermatitis as synonymous with eczema but this is actually not true. Almost any rash can be thought of as a dermatitis based on this definition - including psoriasis, skin cancer, and seborrhea. However, we don't call every rash a dermatitis.
The rash of dermatitis is itchy, red, and may or may not have distinct margins. The specific look of the rash depends on the amount of time it has been present. Acute dermatitis has blisters, subacute dermatitis has scaling and crusting, and chronic dermatitis has lichenification.
There are several distinct types of dermatitis that are delineated by the causative agent or the cellular mechanism responsible for the rash. Examples of specific types of dermatitis are:
- Allergic contact dermatitis - A delayed hypersensitivity reaction involving allergens and antibodies.
- Irritant contact dermatitis - Exposure to irritating chemicals or detergents.
- Atopic dermatitis - An allergic-type reaction that is accompanied by hay fever, asthma, and very dry skin.
- Stasis dermatitis - Occurs on the ankles and lower legs of people with venous insufficiency.
- Diaper dermatitis - A type of irritant dermatitis caused by long exposure of the skin to wet diapers.
- Dyshidrotic dermatitis (pompholyx) A type of dermatitis on the hands or feet that is characterized by redness, scaling, and deep blisters.
- Nummular dermatitis Coin shaped patches that occur anywhere on the body in relation to dry skin.
- Seborrheic dermatitis (cradle cap) Yellow, greasy scales like dandruff on the scalp and hair-bearing areas of the head, neck, and upper chest.
- Autosensitization dermatitis (Id reaction) An itchy rash that occurs in response to an intense inflammatory process somewhere else on the body, especially fungal infections.
- Lichen simplex chronicus A rash caused by long-term scratching of an area producing thickened skin.
Generally, dermatitis is diagnosed clinically, meaning based on the history and appearance of the rash. If possible, the exact type of dermatitis is delineated, but sometimes it is difficult to tell the difference between the dermatitis types. There are very few tests performed that help clarify the type of dermatitis. Some examples of tests that may help with diagnosis are skin tests for contact or atopic dermatitis or a KOH test identifying a fungal infection.
Dermatitis is best treated if the type is known. However, there are measures that can be taken to improve symptoms even if the exact dermatitis type is not known.
- Keep skin as moisturized as possible as dry skin causes cracks in the outer layer inhibiting the barrier function of the skin.
- Reduce itching and scratching with topical medications or antihistamines.
- Avoid irritating and drying substances such as perfumes or harsh detergents.
- Treat other rashes, especially fungal infections, even though they may not seem related.
Topical Steroids and Dermatitis
Topical steroids are often used to treat dermatitis. Topical steroids come in different strengths and can have significant side effects. All topical steroids except Hydrocortisone cream must be prescribed by a health care provider.