Known causes include dry skin, contact with a particular substance, certain drugs or medications, 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 Itching Itching can be very uncomfortable. It is one of the most common reasons people see doctors who specialize in skin disorders (dermatologists). Itching makes people want to scratch. Scratching... read more .)
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 Atopic Dermatitis (Eczema) Atopic dermatitis (commonly referred to as eczema) is chronic, itchy inflammation of the upper layers of the skin that often develops in people who have hay fever or asthma and in people who... read more 
. 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 Contact Dermatitis Contact dermatitis is skin inflammation caused by direct contact with a particular substance. The rash may be itchy, is confined to a specific area, and often has clearly defined boundaries... read more 
, including poison ivy Poison Ivy Poison ivy is an allergic contact dermatitis that causes a very itchy rash caused by exposure to the oil urushiol, which coats the leaves of poison ivy plants. An itchy, red rash and multiple... read more 
; nummular dermatitis Nummular Dermatitis Nummular dermatitis is a persistent, usually itchy rash and inflammation of the skin characterized by coin-shaped spots and scale. (See also Overview of Dermatitis.) The cause of nummular dermatitis... read more 
; stasis dermatitis Stasis Dermatitis Stasis dermatitis is inflammation of the skin of the lower legs resulting from the pooling of blood and fluid. (See also Overview of Dermatitis.) Stasis dermatitis occurs in people who have... read more 
; lichen simplex chronicus Lichen Simplex Chronicus Lichen simplex chronicus is chronic, itchy inflammation of the top layer of the skin caused by repeated scratching, rubbing, or both. Lichen simplex chronicus involves a cycle in which scratching... read more 
; seborrheic dermatitis Seborrheic Dermatitis Seborrheic dermatitis is chronic inflammation that causes yellow, greasy scales and dandruff to form on areas of the skin that have a high number of oil glands such as the scalp and face, along... read more 
; and hand and foot dermatitis Hand and Foot Dermatitis Hand and foot dermatitis is a chronic dermatitis characterized by red, scaly, thickened skin on the hands, the feet, or both. (See also Overview of Dermatitis.) Hand and foot dermatitis often... read more 
), whereas others can occur anywhere (such as atopic dermatitis Atopic Dermatitis (Eczema) Atopic dermatitis (commonly referred to as eczema) is chronic, itchy inflammation of the upper layers of the skin that often develops in people who have hay fever or asthma and in people who... read more ).
Some types of dermatitis have a known cause (such as allergic contact dermatitis Allergic contact dermatitis Contact dermatitis is skin inflammation caused by direct contact with a particular substance. The rash may be itchy, is confined to a specific area, and often has clearly defined boundaries... read more ), 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 Skin tests Doctors can identify many skin disorders simply by looking at the skin. A full skin examination includes examination of the scalp, nails, and mucous membranes. Sometimes the doctor uses a hand-held... read more 
or blood tests. They may take samples of skin and send them to a laboratory (biopsy Biopsy Doctors can identify many skin disorders simply by looking at the skin. A full skin examination includes examination of the scalp, nails, and mucous membranes. Sometimes the doctor uses a hand-held... read more ).
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 (medications that decrease the immune system responses) creams or ointments
Sometimes antibiotics
Sometimes systemic (bodywide) immunosuppressive medications 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 medications. Some people may be helped by exposure to ultraviolet light (phototherapy Phototherapy Psoriasis is a chronic, recurring disease that causes one or more raised, red patches that have silvery scales and a distinct border between the patch and normal skin. A problem with the immune... read more 
).
