Photosensitivity refers to an abnormal cutaneous response to ultraviolet (UV) radiation or visible light and encompasses a broad spectrum of disorders with distinct mechanisms and clinical implications. A practical clinical framework classifies photodermatoses into 5 major categories: 1. Idiopathic photodermatoses. 2. Exogenous-agent photodermatoses. 3. Endogenous-agent photodermatoses (notably porphyrias). 4. Photoexacerbated dermatoses. 5. Photosensitive genodermatoses . Many conditions are triggered primarily by ultraviolet A (UVA), which penetrates deeper into the skin and through window glass, whereas visible-light–driven disease is especially relevant in pigmentary disorders and certain photosensitive dermatoses, requiring tinted/iron-oxide strategies. Tinted sunscreens can be particularly beneficial for visible-light–associated photodermatoses because they can improve spectral coverage that conventional UV filters do not fully address. Photosensitivity may be episodic and benign (eg, seasonal idiopathic photodermatoses) or may signal risk of systemic disease (eg, systemic lupus erythematosus photosensitivity) and metabolic disorders (eg, porphyrias). Therefore, careful classification and evaluation are central to patient safety. In systemic lupus erythematosus, abnormal reactivity to both UV radiation and visible light can be observed during phototesting, supporting the clinical relevance of broader-spectrum avoidance and protection strategies in selected patients.
光敏性是指因暴露于阳光而引发或加重的各种症状、疾病及病症（光皮肤病）。它可分为五类：原发性光皮肤病、外源性光皮肤病、光加重性皮肤病、代谢性光皮肤病和遗传性光皮肤病。多形性日光疹。青少年春季疹。光化性毛囊炎。光化性瘙痒症。日光性荨麻疹。慢性光化性/光敏性皮炎。种痘样水疱病（与爱泼斯坦-巴尔病毒有关）。药物性光敏性：常见的光敏药物有噻嗪类、四环素类、非甾体抗炎药、吩噻嗪类、伏立康唑、奎宁、维莫非尼等多种。光接触性皮炎：由植物、蔬菜、水果中的补骨脂素等光毒性化学物质、化妆品中的香料、防晒化学物质、染料及消毒剂引起。假性卟啉症：由药物和/或肾功能不全诱发。皮肤红斑狼疮（急性、亚急性和慢性变种）。皮肌炎。干燥综合征。毛囊角化病。玫瑰痤疮。黄褐斑。寻常型天疱疮。落叶型天疱疮。特应性皮炎。脂溢性皮炎。银屑病。光化性扁平苔藓。多形红斑。蕈样肉芽肿。迟发性皮肤卟啉症。红细胞生成性原卟啉症。杂合性卟啉症。红细胞生成性卟啉症（冈瑟病）。着色性干皮病。科凯恩综合征。毛发硫营养不良。布卢姆综合征。罗思蒙德·汤姆森综合征。
