Dermatitis is defined as an inflammation of the skin. Contact dermatitis refers to dermatitis that is caused by contact between the skin and a substance. The substance can be an allergen (a substance that provokes an allergic reaction) or an irritant (a substance that damages the skin). Irritants are responsible for about 80 percent of cases of contact dermatitis.

Irritant contact dermatitis occurs when the skin comes in direct contact with a substance that physically, mechanically, or chemically irritates the skin, causing the normal skin barrier to be disrupted.

The most common causes of irritant dermatitis are products used on a daily basis, including soap, cleansers, and rubbing alcohol. People with other skin conditions, dry skin, and light-colored or "fair” skin are at greatest risk, although anyone can develop irritant dermatitis.

Mild irritants cause redness, dryness, small cracks, and itching. Strong irritants may cause swelling, oozing, tenderness, or blisters. The hands are commonly affected, often between the fingers. Irritant dermatitis can also affect the face, especially the thin skin of the eyelids.

The diagnosis of irritant contact dermatitis is usually based upon a person’s history and physical examination. In some cases, a patch test (applying a small amount of a substance to the skin) may be recommended to determine if the dermatitis is allergic or irritant-type. Patch testing should be done by a dermatologist or allergist who is trained in this procedure.

The goal of treatment of irritant contact dermatitis is to restore the normal skin barrier and protect the skin from future injury. Reducing exposure to known irritants is essential. In some cases, simply reducing the use of soap and using an emollient cream or ointment completely alleviates symptoms. Wearing gloves when working with irritants may help as well. In more severe cases, a steroid cream may be recommended

Allergic contact dermatitis occurs when the skin comes in direct contact with an allergen(a substance that provokes an allergic reaction). This activates the body’s immune system, which triggers inflammation. Allergic contact dermatitis can occur after being exposed to a new product or after using a product for months or years such as perfumes and cosmetics, components of rubber, nail polish, and chemicals in shoes (both leather and synthetic). Allergic contact dermatitis can also be triggered by certain medications, including hydrocortisone cream, antibiotic creams and other medication creams.

Symptoms include intense itching and a red raised rash. The rash may blister in severe cases. The rash is usually limited to areas that were in direct contact with the allergen, but a rash can appear in other areas of the body, if the allergen was transferred to those areas on a person’s hands. Washing the allergen away with soap and water can usually prevent this spread. The rash typically appears within 12 to 48 hours of exposure to the allergen, although in some cases it may not appear for up to two weeks. Although less common, the rash can persist for months or years, which makes it difficult to identify the cause of the reaction.

The diagnosis of allergic contact dermatitis is based upon a person’s history and physical examination. If symptoms improve after the allergen is eliminated, this supports the diagnosis. Patch testing may be recommended in some cases and is usually performed by a dermatologist or allergist.

Allergic contact dermatitis usually resolves within two to four weeks after the allergen is eliminated, although it can take more time in some cases. Several measures can minimize symptoms during this time and help to control symptoms in people who have chronic allergic contact dermatitis. Whenever possible, identify and stop all exposure to the allergen. A steroid cream might be prescribed for people with mild to moderate symptoms, and oral steroids reserved for severe forms of dermatitis and these should be prescribed by a dermatologist or an allergy specialist

For people with more bothersome symptoms, wet or damp dressings are recommended, especially when the affected area is oozing fluid and crusting. Such dressings are soothing and relieve itching, reduce redness, gently remove crusts, and prevent additional injury from scratching.