This summary discusses adult patients. Allergic contact dermatitis in children is addressed separately.

Contact dermatitis presents as either allergic or irritant in etiology. While irritant contact dermatitis represents the direct toxic effect of an offending agent on the skin, allergic contact dermatitis (ACD) represents a delayed-type (type IV) hypersensitivity reaction that occurs when allergens activate antigen-specific T cells in a sensitized individual. Consequently, whereas irritant contact dermatitis can occur after one exposure to the offending agent, ACD typically requires repeat exposures before an allergic response is noted. Allergic contact dermatitis can occur 24-48 hours after exposure to the offending agent.

Ocular involvement in ACD can occur in the setting of topical agents (medications or cosmetics), airborne agents, or innocuous transfer of the culprit agent via the fingertips.

With regards to topically applied agents, ACD reactions to medicated drops have been reported, including latanoprost, dorzolamide, and phenylephrine. ACD has also been reported in response to cosmetic products such as acrylate-containing glue used as a false-eyelash adhesive. Many eye shadow products include metals, which are top-ranking allergens in patients with eyelid dermatitis.

Nickel sulfate and gold are top-ranking allergens in periorbital dermatitis. Accidental transfer may occur when hands are contaminated by prior contact with metal products including jewelry. Similarly, fragrances can be transferred from the hands to the face. Eyelid dermatitis can also be seen due to allergens in artificial fingernails.

Airborne exposures have been implicated in occupational ACD, such as a reported case of persistent periorbital ACD in a dental technician due to rubber accelerator found in a colleague's protective gloves. These airborne exposures can sometimes be associated with respiratory difficulty, as described in cases of airborne ACD reactions to methylisothiazolinone.