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Overview of Dermatitis


By Karen McKoy, MD, MPH, Assistant Clinical Professor, Dermatology, Harvard Medical School; Senior Staff, Lahey Clinic Dermatology

Dermatitis (sometimes called eczema) is inflammation of the upper layers of the skin, causing itching, blisters, redness, swelling, and often oozing, scabbing, and scaling.

  • Known causes include dry skin, contact with a particular substance, certain drugs, varicose veins, and constant scratching.

  • Typical symptoms include a red itchy rash, blisters, open sores, oozing, crusting, and scaling.

  • The diagnosis is typically based on symptoms and confirmed by results of skin tests or skin samples or the presence of suspected drugs, irritants, or infection.

  • Avoiding known irritants and allergens reduces the risk of dermatitis.

  • Treatment depends on the cause and the specific symptoms.

Dermatitis is a broad term covering many different disorders that all result in a red, itchy rash. The term eczema is sometimes used for dermatitis or for atopic dermatitis. Skin infections, such as fungal infections, are not classified as dermatitis.

Some types of dermatitis affect only specific parts of the body (such as contact dermatitis, nummular dermatitis, stasis dermatitis, or pompholyx), whereas others can occur anywhere (such as atopic dermatitis or exfoliative dermatitis).

Some types of dermatitis have a known cause (such as allergic contact dermatitis), whereas others do not (such as nummular dermatitis).

Despite its type or cause, dermatitis is always the skin's way of reacting to severe dryness, scratching, an irritating substance, or an allergen. Typically, that substance comes in direct contact with the skin, but sometimes the substance is swallowed. In all cases, continuous scratching and rubbing may eventually lead to thickening of the skin (lichenification).

Dermatitis may be a brief reaction to a substance, lasting for just a few hours or for only a day or two.

Chronic dermatitis persists over a period of time. The hands and feet are particularly vulnerable to chronic dermatitis, because the hands are in frequent contact with many foreign substances and the feet are in the warm, moist conditions created by socks and shoes. Chronic dermatitis may represent a contact dermatitis, pompholyx, or other dermatitis that has been inadequately diagnosed or treated, or it may be one of several chronic skin disorders of unknown origin.

Symptoms of Dermatitis

Dermatitis causes

  • Redness

  • Swelling

  • Oozing

  • Crusting

  • Scaling

  • Blisters (sometimes)

  • Thickening of skin

Itching is common. Open sores (ulcers) may develop.

Chronic dermatitis causes cracks and blisters in the skin, and any type of chronic dermatitis may lead to bacterial infection.

Diagnosis of Dermatitis

  • Skin or blood tests or both

  • Sometimes biopsy

Doctors base the diagnosis of dermatitis on the person's symptoms and on what the rash looks like and where it appears on the body. Doctors try to determine whether the person has swallowed or applied any drugs to the skin, has come in contact with an irritating substance, has an allergy, or has an infection.

To confirm the diagnosis, doctors may do certain tests, such as a patch test or use test, or blood tests. They may take samples of skin and send them to a laboratory (biopsy).

Prevention of Dermatitis

  • Avoidance of triggers

To reduce the risk of dermatitis, people should avoid known allergens and irritating substances (triggers).

Treatment of Dermatitis

  • Supportive care (such as moisturizers and dressings, and antihistamines for itching)

  • Topical corticosteroids

  • Sometimes antibiotics or other drugs

  • Sometimes ultraviolet (UV) light therapy

Dermatitis treatment depends on the cause and the specific symptoms. For example, doctors may give people moisturizers or corticosteroid creams to relieve itching. Some people may be given antibiotics by mouth or injections of certain drugs. Some people may be helped by exposure to ultraviolet light (see Phototherapy).

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