Used in photochemotherapy (PUVA therapy) for skin disorders like psoriasis, vitiligo, and eczema. When activated by UVA light, it binds to DNA and inhibits rapid cell division, helping control skin cell overgrowth. Also used in research for its photosensitizing properties and in some cosmetic applications to repigment skin. Requires careful dosing due to potential side effects like skin sensitivity and increased risk of skin cancer with long-term use.