Used in photodynamic therapy (PDT) for the treatment of skin conditions such as actinic keratosis and certain types of non-melanoma skin cancers. It acts as a prodrug that is metabolized in cells to protoporphyrin IX, a photosensitizer. When exposed to specific wavelengths of light, protoporphyrin IX generates reactive oxygen species that selectively destroy abnormal cells. Its topical application allows targeted treatment with minimal systemic absorption, making it a safe and effective option in dermatology. Also investigated for use in fluorescence diagnosis due to the natural fluorescence of accumulated protoporphyrin IX in diseased tissues.