Background: One of the main strategies in the prevention of photodermatoses is the use of topical sunscreens, which sometimes must be applied together with topical drugs specific for the dermatosis with the possibility that the efficacy of the sunscreen may be altered.

Objectives: The aim of this study was to analyse whether the efficacy of the sunscreen could be affected when applied together with topical drugs routinely used in patients with photodermatoses and whether there is any variation when they are applied before or after the drug.

Methods: Ninety-three volunteer patients with photodermatoses participated. Very high SPF sunscreens were used with corticosteroids, antibiotics and topical antifungals as active ingredients. Paravertebral areas were delimited in each individual and the sunscreen was applied alone and in association with a drug in different sequential order. Ultraviolet reflectance photography and image analysis were used to compare the level of UV absorption by the sunscreen/drug combinations in the different areas.

Results: UV reflectance analysis showed no difference in the efficacy of the sunscreen applied before or after the various drugs used. In the antifungal group, a significant increase in the effect of the sunscreen was observed when the antifungal was applied first.

Conclusions: The efficacy of sunscreens was not altered by combined use with corticosteroids, antibiotics or topical antifungals. These results are of great relevance for patients with photodermatosis who often have to combine these active ingredients with photoprotection.