Contact dermatitis is a skin condition that occurs when the skin comes into direct contact with an irritant or allergen. This can lead to symptoms such as redness, itching, and swelling. Common irritants include soaps, detergents, and certain metals like nickel. Allergic reactions can be triggered by substances like poison ivy or fragrances. There are two main types of contact dermatitis: irritant contact dermatitis and allergic contact dermatitis. Irritant contact dermatitis results from exposure to a harmful substance, while allergic contact dermatitis occurs when the immune system reacts to an allergen. Treatment often involves avoiding the triggering substance and using topical medications to relieve symptoms.