Ultraviolet light is needed to activate production of vitamin D in the body, which prevents rickets, osteomalacia and osteoporosis. It may also affect some cancers and immune disorders.

• 在人体内部，紫外线被用来刺激维生素D的生成，这种维生素能预防驼背、骨软化和骨质疏松症等骨骼问题。另外，它对某些癌症和免疫系统的疾病也有影响。