The sun delivers energy as electromagnetic radiation, characterised by specific wavelengths. The spectrum of the electromagnetic radiation emitted by the sun and able to reach the Earth’s surface ranges between 290 and 300 nm.
In particular, the electromagnetic radiation (EMR) with photo-biological interest are detailed in Table 1.
Despite the innumerable and beneficial effects of sun rays on our physical and psychological state, the role of UV rays in the adverse effects at systemic, ocular and skin level is becoming more and more evident. In the past, dermatologists and cosmetic formulators used to focus their attention on UVB protection, as UVB radiation was held responsible for immediate and evident skin damages, such as erythema or sunburn.1 However, both the biological damage caused by UVB radiation on the DNA of keratinocytes and by the longer wavelength UVA radiation on the dermis, are asymptomatic, tend to increase over time and show their effects after many years. UVB radiation induces carcinogenesis too.
After penetrating the dermis, UVA radiation causes the release of free radicals which damage nuclear DNA, cell membranes, functional and structural protein of skin cells and causes the onset of elastosis as well as possible cancerous changes.
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