Merck Manual

Please confirm that you are not located inside the Russian Federation

honeypot link

Overview of Dermatitis



Thomas M. Ruenger

, MD, PhD, Georg-August University of Göttingen, Germany

Last full review/revision Apr 2021| Content last modified Apr 2021
Click here for the Professional Version
See What's New in this Topic
  • Poison ivy has been revised and now has separate sections for symptoms, diagnosis, prevention, and treatment.

Dermatitis 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, and varicose veins.

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

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

  • Avoiding known irritants and allergens (substances that cause an allergic reaction) 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, including poison ivy; nummular dermatitis; stasis dermatitis; lichen simplex chronicus; seborrheic dermatitis; and hand and foot dermatitis), whereas others can occur anywhere (such as atopic dermatitis).

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

Chronic dermatitis persists over a long period of time. The hands are particularly vulnerable to chronic dermatitis, because the hands are in frequent contact with many foreign substances. Chronic dermatitis can have many different causes. Chronic scratching and rubbing because of itching often results in thickening of the skin (lichenification).

Symptoms of Dermatitis

Dermatitis causes

  • Redness

  • Itching

  • Scaling

  • Swelling

  • Oozing

  • Crusting

  • Blisters (sometimes)

  • Thickening of skin, or lichenification (in chronic dermatitis)

Chronic dermatitis often results in thickening of skin and cracks in the skin. Any type of dermatitis may be complicated by an infection.

Diagnosis of Dermatitis

  • A doctor's examination

  • 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 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 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 or other immunosuppressive (drugs that decrease the immune system responses) creams or ointments

  • Sometimes antibiotics

  • Sometimes systemic (bodywide) immunosuppressive drugs or injections

  • 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

Test your knowledge

Ichthyosis is a form of severe dry skin that causes it to scale (build up excessive dry skin cells) and flake. Ichthyosis ranges in severity from mild to disfiguring, and may be either inherited or acquired. During which of the following time periods does inherited ichthyosis usually first manifest?
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest

Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID