Photoallergic contact dermatitis is one of the important parts of photodermatoses. The investigation of choice is photopatch testing. However, reports with photopatch test results from Asian countries are scarce.

The aim of a new study published in Photodermatology, Photoimmunology & Photomedicine was to determine the prevalence of positive photopatch test reactions and to ascertain the common photoallergens among Thai patients during 1998-2018.

This was a retrospectively review of records of 339 patients who were clinically suspected of having photoallergic contact dermatitis and had undergone photopatch testing.

The findings accounted 44 photoallergic contact reactions in 38 patients (11.2%). Positive photoallergic reactions were mainly detected with organic ultraviolet filters and fragrances.

It was concluded that organic ultraviolet filter chemical, especially benzophenone-3 and fragrances were found to have a high prevalence of photoallergic contact reactions. It was stated that monitoring of the photoallergens employed in photopatch tests should be conducted periodically to provide the best patient care.

Source: Photodermatology, Photoimmunology&Photomedicine. 2020 Aug 20. doi: 10.1111/phpp.12603.