fototoksisia

Fototoksisia refers to a type of adverse skin reaction that occurs when a chemical substance on or in the skin is activated by light, typically ultraviolet (UV) radiation. This activation leads to the generation of reactive oxygen species or other harmful molecules that damage skin cells. The resulting reaction can resemble a sunburn, appearing as redness, swelling, itching, and sometimes blistering.

There are two main types of phototoxic reactions: photoallergic and phototoxic. Phototoxic reactions are more common and occur when a chemical absorbs UV light and directly damages cells. This can happen with a wide range of substances, including certain medications (like tetracyclines, NSAIDs, and diuretics), topical treatments (such as retinoids and coal tar), and even some natural compounds found in plants (like those in citrus fruits, figs, and parsley). The reaction is dose-dependent, meaning a higher concentration of the substance or more intense light exposure will lead to a more severe reaction.

Photoallergic reactions, in contrast, involve an immune system response. The chemical is altered by UV light into a form that the immune system recognizes as foreign, triggering an allergic reaction. This type of reaction is less common and is not dose-dependent in the same way as phototoxic reactions. Symptoms can include itching, eczema-like rashes, and sometimes hives.

Prevention of phototoxic reactions involves avoiding exposure to known photosensitizing agents and minimizing sun exposure, particularly during peak UV hours, if one is using or has been exposed to such substances. Sunscreen that blocks both UVA and UVB radiation can also be helpful. If a reaction occurs, treatment typically involves avoiding further exposure to the offending agent and the sun, and applying cool compresses or topical corticosteroids to alleviate symptoms.