Contact dermatitis is a localized rash or irritation of the skin caused by contact with a foreign substance. The resulting red, itchy rash isn't contagious or life-threatening, but it can be very uncomfortable.
Contact Dermatitis Causes
There are 2 types of contact dermatitis: allergic and irritant. Irritant contact dermatitis is more common of the two.
- Allergic contact dermatitis. This type of dermatitis is caused by a reaction to substances called allergens. The resulting reaction is the body's response to the sensitive agent. Allergic contact dermatitis produces a red rash, bumps and sometimes blisters when severe. Common allergens include rubber, metals such as nickel, costume jewelry (nickel), perfume, cosmetics, hair dyes and weeds, including poison ivy. It may take several years for an allergy to develop. Once an allergy has developed to a specific substance, however, it remains for life. Exposure to even a small amount of the allergen will reliably result in skin eruption.
- Irritant contact dermatitis. This type of dermatitis results from repeated contact with a substance, such as soap, cosmetics or skin products, including deodorant, which irritates the skin. The exposure produces red, dry itchy patches usually on the hands, fingers and face. Some substances, such as bleach or strong acids, can cause irritant contact dermatitis after just one exposure. These substances typically remove oil and the protective barriers from the skin.
- People with other skin conditions, such as eczema, are most likely to develop contact dermatitis.
The cause of contact dermatitis is direct contact with one of many irritants or allergens. These include:
- Strong detergents or soaps
- Skin cleaning products
- Cosmetics or makeup
- Clothing or shoes
- Household cleaning products
- Formaldehyde and other chemicals
- Metals, such as nickel
- Perfume or fragrances
- Weeds and plants, such as poison ivy or poison oak
- Medicinal lotions, such as antihistamines, antibiotics or antiseptics
- Rubber or latex
Some substances are both allergens and irritants. Examples include ingredients in soaps, detergents and some cosmetics.
It takes a greater amount of an irritant over a longer time to cause dermatitis than it takes for an allergen. If a person is sensitized to an allergen, just brief exposure to a small amount can cause contact dermatitis. If re-exposure to a substance always results in dermatitis, then this substance is more likely an allergen than an irritant. The allergen might be something that the person had been in contact with for years without trouble until now. Once an allergy has developed to a specific substance, however, it remains for life.
Some substances only cause dermatitis when they contact skin exposed to sunlight (photocontact dermatitis). Typical examples include shaving lotion, sunscreens, ointments containing sulfa drugs, some perfumes and coal tar products. Other causes of contact dermatitis may be airborne, such as ragweed pollen and insecticide spray.
Occupational contact dermatitis occurs when a person is exposed to allergens or irritants on the job. Frequent exposure to water, friction, chemicals, fuels, dyes, cleaning agents, industrial solvents or dust (for example, cement dust, sawdust or paper dust) can lead to contact dermatitis.
Contact Dermatitis Symptoms
Signs and symptoms of contact dermatitis include:
- Red rash or bumps
- Itching, which may be severe
- Dry, red patches, which may resemble a burn
- Blisters and draining fluid from the involved skin in severe cases
- Skin rash limited to the exposed area
Screening and Diagnosis of Contact Dermatitis
The diagnosis of contact dermatitis is usually suspected based on the history provided, and after a thorough physical examination. If the cause of the dermatitis isn't apparent or if it recurs, Dr. Alaiti will recommend skin patch testing (contact delayed hypersensitivity allergy test).
During a patch test, small quantities of potential allergens are applied to small patches, which are then placed on the skin to check for a reaction. The patches remain on the skin for two to four days before being evaluated again. If the person is allergic to a particular substance being tested, a raised bump or a reaction limited to the skin just beneath the patch will develop.
Treatment of Contact Dermatitis
Contact dermatitis treatment consists primarily of identifying what's causing the irritation and then avoiding it. If this is done, it may take two to four weeks for the rash and irritation to clear up. In mild cases, self-care measures, such as using creams containing hydrocortisone or applying wet dressings, can help relieve redness and itching. In moderate to severe cases, Dr. Alaiti will prescribe topical medications, oral corticosteroids and antihistamines in order to reduce the inflammation and relieve the intense itching.
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