**8. Conclusion**

Until now, the role of photosensitizers involving photocatalysis in the skin components is poorly understood in photoaging. In this review, we focused on the hydrogen peroxide generated by the UVA-photosensitization reaction by multiple photosensitizers, such as riboflavin, amino acids and vitamins. We also introduced a simple screening method for discovering compounds that are effective for UVAphotosensitization, using ergothioneine as an example.
