photoallergic dermatitis (MONDO_0006596, a Monarch Disease Ontology entry) is a delayed hypersensitivity involving the reaction between sunlight or other radiant energy source and a chemical substance to which the individual has been previously exposed and sensitized. It manifests as a papulovesicular, eczematous, or exudative dermatitis occurring chiefly on the light-exposed areas of the skin. Also known as: photoallergic contact dermatitis, photoallergic eczema.