''Photocontact dermatitis''
Toxic or allergic reaction when skin that has been exposed to certain chemicals gets exposed to sunlight. eg some sunscreen, coal tar, fragrance, insecticides
Phototoxic - direct damage of cells by photo activated agent - looks like bad sunburn
Photoallergic - cell mediated response where allergen is the light-activated agent - looks more like eczema but only in the exposed area

''Phytophotodermatitis''
A photocontact dermatitis where the agent comes from certain plants - eg Hogweed
clinically blistering and swelling - may be minutes but more usually 48-72 hours post exposure, may leave behind postinflammatory hyperpigmentation (which may be only change observed)

Management
Avoid agent and sun exposure
Cold compress
Topical steroid - or oral steroids