Is It Really Photosensitivity? What It Is, How to Prevent It, and How to Treat It

Photoallergy, or photosensitivity, refers to an atopic (allergic) skin reaction primarily triggered by exposure to ultraviolet (UV) radiation, though not exclusively. It can also result from exposure to rehab lamps, laser radiation (e.g., during hair or tattoo removal), or visits to a solarium. It is essential to note that a photoallergic reaction does not occur spontaneously—it requires the presence of a photosensitizer (photoucher). A defining feature of these agents is the presence of chromophores, which enable the absorption of radiation and the initiation of undesired processes during the allergic response.

Upon reaching the skin, sunlight penetrates deeply into the epidermis, where chromophores in photosensitizers absorb its energy. Consequently, photosensors undergo transformation into haptens (allergens) that trigger an allergic skin response. The photosensitivity reaction typically manifests as inflammation, itching, skin peeling, pigmentation disorders, and contact dermatitis with papules. Notably, these changes are not confined to UV-exposed areas but may also appear on other body regions, including covered skin. Symptoms generally appear 1–2 days after sun exposure.

The majority of photosensitizers are medications whose active ingredients can induce undesirable skin changes when exposed to UV radiation. Individuals undergoing long-term pharmacological treatment, particularly during spring and summer, as well as those receiving procedures that may trigger photosensitivity (e.g., laser hair removal) should consult their physician or pharmacist regarding the risk of allergic reactions. Potential photosensitizing medications include antibiotics, antifungals, acne treatments, nonsteroidal anti-inflammatory drugs, antihistamines, psychotropic drugs, and antidepressants. Certain herbs and dietary supplements, despite their natural origin, contain potent photosensitizers capable of inducing severe allergic responses. These include mountain arnica, common nettle, medicinal aloe, chamomile, and horsetail. It is also crucial to consider retinoids, derivatives of vitamin A, commonly used in acne therapy. These compounds promote the exfoliation of dead skin cells, regulate sebum production, and enhance keratinocyte differentiation, thereby increasing skin susceptibility to UV radiation, which may result in allergic reactions, sunburn, and skin damage.

Photoallergy is frequently confused with phototoxicity, though they are distinct phenomena. Photoallergy is an allergic response that typically occurs at least 24 hours after UV exposure and results in skin changes throughout the body, including non-exposed areas. Phototoxicity, on the other hand, is an entirely different issue, with a distinct reaction mechanism. Sunlight causes photosensitizers to release excessive amounts of reactive oxygen species (free radicals), which damage cells. This means that the interaction between the photosensitizing substance and UV radiation leads to skin damage, such as swelling, blisters, or redness. Another key difference is the reaction time – phototoxic reactions occur within minutes or hours, and skin changes are limited to exposed areas. Examples of substances that induce phototoxicity include antiarrhythmic drugs, antimalarial medications, cytotoxic agents, and plants like lovage, St. John's wort, carrots, parsley, and greater burnet.

Similar to other allergic responses, it is crucial to minimize factors that may trigger photosensitivity. There are two primary approaches: replacing photosensitizing agents and reducing UV exposure. Skin changes often occur, necessitating the use of antihistamines, corticosteroids, and skin care products with natural ingredients. In severe cases, compresses with boric acid or seawater may be applied.