Photosensitizing agents can be found in a variety of sources, including medications, plants, and industrial chemicals. Some well-known photosensitizing drugs include antibiotics like tetracyclines and fluoroquinolones, diuretics such as thiazides, and non-steroidal anti-inflammatory drugs (NSAIDs) like naproxen. Additionally, plants like St. John's Wort contain compounds that can induce photosensitivity.