ABSTRACT
Ultraviolet (UV) radiation emitted by the sun is divided into three bands: UVA, UVB, and UVC. UVA is further subdivided into UVA2 (320-340 nm) and UVA1 (340-400 nm). The nitrogen and oxygen molecules in the ozone layer absorb UVC, so only UVA and UVB reach the Earth’s surface. Side effects of UV exposure have been well studied and can be divided into acute and chronic effects. The most well-recognized, acute effect is erythema, which is the predominant biologic effect of UVB and, to a lesser extent, UVA2. UVB exposure also induces cutaneous vitamin D synthesis. Immediate and persistent pigment darkening (PPD) and delayed tanning are caused predominantly following UVA exposure, although in dark-skinned individuals, it can be induced by exposure to visible light (Mahmoud et al. 2010). Epidermal hyperplasia occurs within days of UV exposure. Chronic effects are photoaging and photocarcinogenesis.
