Photosensitivity is one of the most common cutaneous
adverse drug reactions. There are two types of drug-induced photosensitivity:
photoallergy and
phototoxicity. Currently, the number of
photosensitization cases is constantly increasing due to excessive exposure to sunlight, the aesthetic value of a tan, and the increasing number of photosensitizing substances in food, dietary supplements, and pharmaceutical and cosmetic products. The risk of photosensitivity reactions relates to several hundred externally and systemically administered drugs, including nonsteroidal anti-inflammatory, cardiovascular, psychotropic, antimicrobial,
antihyperlipidemic, and
antineoplastic drugs. Photosensitivity reactions often lead to hospitalization, additional treatment, medical management, decrease in patient's comfort, and the limitations of drug usage. Mechanisms of drug-induced photosensitivity are complex and are observed at a cellular, molecular, and biochemical level. Photoexcitation and photoconversion of drugs trigger multidirectional biological reactions, including oxidative stress,
inflammation, and changes in
melanin synthesis. These effects contribute to the appearance of the following symptoms:
erythema, swelling,
blisters, exudation, peeling, burning,
itching, and
hyperpigmentation of the skin. This article reviews in detail the chemical and biological basis of drug-induced photosensitivity. The following factors are considered: the chemical properties, the influence of individual ranges of sunlight, the presence of
melanin biopolymers, and the defense mechanisms of particular types of tested cells.