Exogenous factors - Photoallergens

Photoallergy is a delayed type allergic reaction (type IV allergy according to Coombs and Gell) to an exogenous agent consisting of a sensitisation phase, an incubation period after the first exposure, and a clinical reaction following any subsequent contact to the allergen in association with sunlight. The pathogenesis is equal to that of allergic contact dermatitis, with the exception that UV-light is required to induce photoallergen formation. Common photoallergens include suncreens, fragrances such as musk and sandalwood oil and antibacterial agents such as chlorhexidine.