Ultraviolet radiation with a wavelength of 290-400 nm reaches the Earth's surface. These are divided into shorter, so-called erythematogenic UVB radiation (290 - 320 nm) and longer UVA radiation (320 - 400 nm). The normal ozone layer absorbs radiation of a shorter wavelength, UVC (<290 nm). We associate the sun with health and well-being. The beneficial effects of sunlight are related to the visible and infrared spectrum. However, the only beneficial effect of UV radiation is the synthesis of vitamin D3 in the skin, for which minimal doses of UVB are sufficient for induction.