Merck Manual

Please confirm that you are not located inside the Russian Federation

Loading

Overview of Dermatitis

(Eczema)

By

Mercedes E. Gonzalez

, MD, University of Miami Miller School of Medicine

Last full review/revision Mar 2018| Content last modified Mar 2018
Click here for the Professional Version
Topic Resources

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.

(See also Itching.)

Dermatitis is a broad term covering many different disorders that all result in a red, itchy rash. Eczema is synonymous with dermatitis but is often used to mean 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).

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

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.

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. In all cases, continuous scratching and rubbing may eventually lead to thickening of the skin (lichenification).

Symptoms

Dermatitis causes

  • Redness

  • Swelling

  • Oozing

  • Crusting

  • Scaling

  • Blisters (sometimes)

  • Thickening of skin (in chronic dermatitis)

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

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

Diagnosis

  • 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 have the person try the suspect product on a small area of skin to see if a rash occurs (a "use test"), or blood tests. They may take samples of skin and send them to a laboratory (biopsy).

Prevention

  • Avoidance of triggers

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

Treatment

  • 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 (phototherapy).

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
Others also read

Also of Interest

Videos

View All
Skin Cancer
Video
Skin Cancer
The skin is the largest organ of the body. It serves many important functions, including protecting...
3D Models
View All
Lymphangitic Streak
3D Model
Lymphangitic Streak

SOCIAL MEDIA

test
iOS Android
iOS Android
iOS Android
TOP