Fototoksinen

Fototoksinen, also known as phototoxicity, refers to a type of adverse reaction that occurs when a photosensitizing substance is ingested or applied to the skin, and the individual is subsequently exposed to light, typically ultraviolet (UV) radiation. This interaction can lead to exaggerated sunburn-like reactions, rashes, and skin damage. The severity of the phototoxic reaction depends on the concentration of the photosensitizing agent, the duration and intensity of light exposure, and individual susceptibility.

Photosensitizing substances can be broadly categorized into exogenous and endogenous. Exogenous photosensitizers are external agents that include certain medications (such as tetracyclines, sulfonamides, diuretics, and nonsteroidal anti-inflammatory drugs), topical agents (like retinoids, essential oils, and some sunscreens), and even certain plants (phytophotodermatitis, commonly seen with celery or parsnip sap). Endogenous photosensitizers are substances produced by the body, often due to metabolic disorders. Porphyrias are a group of genetic disorders that result in the accumulation of porphyrins, which can cause extreme photosensitivity.

The mechanism behind phototoxicity involves the photosensitizing agent absorbing light energy. This absorbed energy then triggers photochemical reactions, leading to the generation of reactive oxygen species (ROS) or free radicals. These ROS can damage cellular components, including DNA, proteins, and cell membranes, resulting in inflammation and tissue injury. Unlike photoallergic reactions, phototoxicity is not an immune-mediated response and can occur in anyone exposed to sufficient amounts of the photosensitizer and light. Treatment typically involves avoiding the offending substance and limiting further light exposure.