Used primarily in photochemotherapy, specifically in the treatment of skin conditions like psoriasis and vitiligo. It works by sensitizing the skin to ultraviolet (UV) light, enhancing the therapeutic effects of UV exposure. When applied topically or taken orally, it binds to DNA in skin cells. Upon UV light activation, it forms cross-links in DNA, slowing down excessive cell proliferation in conditions like psoriasis. In vitiligo, it helps repigment the skin by stimulating melanocyte activity. It is also being researched for its potential in treating cutaneous T-cell lymphoma due to its ability to target abnormal lymphocytes under UV light. Proper dosage and controlled UV exposure are critical to avoid adverse effects like burns or increased skin cancer risk.