Phototoxic Dermatitis Induced by Doxycycline and Plant-Derived Furocoumarins: Different Mechanisms, Shared Clinical Consequences
Abstract Phototoxic dermatitis is a non-immunologic inflammatory reaction that occurs when photosensitizing substances interact with ultraviolet A (UV-A) radiation. It differs fundamentally from an allergic drug reaction, which is immune-mediated and may present with life-threatening symptoms such as airway swelling, difficulty breathing, or generalized urticaria requiring immediate medical attention. Both pharmaceutical agents, such as doxycycline and therapeutic psoralens, and naturally occurring plant compounds including furocoumarins found in giant hogweed ( Heracleum mantegazzianum ), celery, parsley, and citrus fruits can induce phototoxic injury. Although the clinical appearance may resemble severe sunburn, the underlying mechanisms differ. Doxycycline primarily causes reactive oxygen species (ROS)-mediated oxidative injury, whereas furocoumarins undergo UV-A activation and form covalent DNA adducts, resulting in more profound and often longer-lasting cellular damage. The clinic...