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Skin exposure to the sun may lead to short-term responses clinically characterized by sunburn and tanning, as well as to long-term outcomes such as skin cancers, photosensitive dermatoses, immunosuppression and acceleration of skin photoaging. There are various factors influencing the effects of ultraviolet radiation. This review presents these possible factors to further realize the damage of ultraviolet rays and its protection, including local ultraviolet ray climatology, sun exposure behaviors and attitudes, relationship between sun exposure and sunburn, etc. significantly contributes to extrinsic skin aging. [Key word] Ultraviolet radiation; Sun exposure; Sun protection; Sunscreen