Allergic Contact Dermatitis
This condition develops when the immune system reacts to an allergen as if it were harmful. It is common for the immune system to become sensitized to an allergen after repeated exposures. Once sensitized, even a trace of the allergen might cause a reaction. Certain metals, such as nickel, certain fragrances, latex, and some plants, such as poison ivy, are common allergens.
Irritant Contact Dermatitis
This is the most frequent form and develops when the skin comes into direct contact with a material that damages the skin’s outer layer. Irritating contact dermatitis, unlike allergic contact dermatitis, does not involve an immune system response and can occur with a single encounter with an irritant. Chemicals such as detergents, acids, and solvents are common irritants.