Irritant contact dermatitis is a reaction caused by direct physical or chemical injury to the epidermis. The damage caused by an irritant leads to inflammation, manifested in the skin as erythema, edema, and scaling. Irritant contact dermatitis should be differentiated from true allergic contact dermatitis, which is a delayed type-IV hypersensitivity (immune) reaction. Early in the course of irritant contact dermatitis, patients typically complain of a burning or stinging sensation; the symptoms and skin eruption usually follow the exposure by hours if the irritant is strong (whereas in allergic contact dermatitis, symptoms are usually delayed by approximately 2 days following exposure). As the irritation becomes chronic and the skin continually inflamed, pruritus can become a predominant symptom.

The hands are the most common location for irritant contact dermatitis, although any body surface may be involved. Eyelid areas are also easily affected due to the very thin skin of the region and the unwitting transmission of irritant substances by the hands. (See also Hand dermatitis.)

Patients with a history of atopic dermatitis are particularly predisposed. Environmental factors include repeated exposure to water or frequent hand washing, soaps and solvents, fiberglass, mild acids, and alkalis. Dry air can also predispose to irritant contact dermatitis. Exposures are frequently occupational. High-risk jobs include cleaning, health care, food preparation, and hairdressing. Irritant contact dermatitis can occur at any age. It is more common in women.