Contact dermatitis is a skin reaction caused by a substance or physical insult from the outside “in contact” with the skin surface.
There are 2 main types of contact dermatitis:
Irritant Contact Dermatitis
Irritation is direct outer skin damage, which can occur from excessive dryness, wetness, soap, friction, rubbing of the skin, bleach, alcohol, or solvents touching the skin surface. Any of these, or a combination, can trigger redness, stinging, and itching. The immune system is not a trigger for this type of skin reaction, and the diagnosis is based on exposure history and appearance of the skin. Examples of irritant contact dermatitis are “winter dry skin”, chapped lips, hand eczema from frequent handwashing, or chafing. Some types of diaper rash are due to irritation.
Allergic Contact Dermatitis
An otherwise harmless substance in contact with the skin can trigger an immune or “allergic” reaction, causing a red, usually VERY itchy dermatitis. It does not have to be anything “new” in contact with the skin, and can occur for the first time at any age. In a sense, your body’s immune system is doing its job to alert you that something is in contact with the skin! Even ingredients in baby products can cause reactions of this type, but only in very few individuals.
Common examples of allergic contact dermatitis are poison ivy or oak dermatitis and nickel reactions causing a rash at sites of metal jewelry touching the skin. Allergic contact dermatitis can occur to gloves, skin product ingredients, fragrances and “botanicals”, chemicals used in the workplace, and even topical medications.
If the provider suspects an allergic contact dermatitis, a type of allergy testing called “patch testing” may be ordered to help figure this out.