It routinely is included in the safety evaluation of raw materials by the Research Institute for Fragrance Materials and several methods for identifying phototoxic compounds have been reported. Both in vitro and in vivo methods are employed currently. This identifies potential phototoxic substances before they are marketed. Photopatch testing may be performed if photoallergy is strongly suspected. The results are evaluated at several time intervals, according to an established score based on the skin reaction pattern.
Adequate controls are imperative to differentiate phototoxicity from photoallergy.
In phototoxicity, all controls will have a positive response, whereas in photoallergy, controls should be negative. The histopathological findings in berloque dermatitis are identical to other phototoxic reactions, an irritant cutaneous response. The epidermal changes consist of keratinocyte necrosis, intercellular and intracellular edema, and intraepidermal blisters. In severe cases, these blisters may rupture, resulting in subepidermal bullae. Neutrophils enter the epidermis at an early stage.