Causes of Contact Dermatitis
Why does contact dermatitis occur? The specific cause will depend on whether a person has allergic contact dermatitis or irritant contact dermatitis. In the case of allergic contact dermatitis, a person experiences an allergic reaction to something that comes in contact with the skin. Irritant contact dermatitis is caused by irritation of the skin (through contact with solvents or soap, for example) or repeated exposure to wet conditions.
The cause of contact dermatitis is exposure to substances in the environment that come in contact with the skin. There are two types of contact dermatitis -- irritant contact dermatitis and allergic contact dermatitis. The specific causes of contact dermatitis will vary based on the type of contact dermatitis a person has.
Allergic contact dermatitis may look similar to irritant contact dermatitis, but the reason the rash develops is different. For allergic contact dermatitis, the cause is an allergic reaction to a particular substance that comes in contact with the skin.
Allergies occur when the body's immune system reacts to a normally-harmless substance -- one that does not bother most people. People who have allergies are often sensitive to more than one substance. Some examples of substances that can cause allergic contact dermatitis include:
- Cosmetics, such as hair sprays, shampoos, makeup, sunscreens, perfumes, shaving cream, nail polish, lipstick, deodorants, and acne medications
- Dyes or fabric finishes
- Laundry detergent
- Fragrances, such as perfume or aftershave lotion
- Certain metals, such as nickel
- Chemicals in the air, such as sprays, perfumes, chemical dusts, or plant pollen (ragweed)
- Poison ivy
- Poison oak
- Poison sumac
- Cashew nuts (which contain a chemical similar to poison ivy)
- Formaldehyde (found in certain shampoos and cosmetics)
- Certain medicines placed on the skin, such as certain antibiotics
- Rubber, such as the rubber contained in latex surgical gloves, adhesives, shoes (which can cause shoe dermatitis), or the elastic in bras and underwear.