Sun: friend or enemy?

Exposure to ultraviolet radiation (UVR) is the most significant environmental risk factor for all types of skin cancer.UVR is defined as the radiation between 100 and 400 nanometers (nm) in length and are characterized further according to wave length into ultraviolet: A (315–400nm), B (280–315 nm) and C (100–280nm). The stratospheric ozone layer totally blocks UVC radiation and UVB wavelengths below 295nm, so 90–95% of the UVA reaches the Earth’s surface.A wide variety of skin disease may arise in exposed areas and are at the same time induced or exacerbated by irradiation from the sun.Well-known acute clinical effects of UVR in the skin are in ammation (sunburn) and reactive epidermal hyperplasia thickening of stratum corneum and tanning. Chronic changes include photoaging immunosuppression and skin cancer.Skin cancer are mainly divided into melanoma and non-melanoma skin cancers (NMSCs), the latter including basal cell carcinomas (BCC) and squamous cell carcinomas (SCC). Melanoma is responsible for most of the cancer related mortalities, and NMSCs are typically described as having a more benign course with locally aggressive features.Photoprotection is the primary strategy against photoaging, photodermatoses and photocarcinogenesis. Recommended measures include avoiding exposure to the sun during hours of peek UV irradiation, wearing protective clothing against ultraviolet radiation penetration and sunglasses and applying an appropriate topical sunscreens prior and during to exposure.Today topical sunscreens are divided into two broad categories: organic (formerly designated chemical) and inorganic (formerly designated physical) agents. Organic sunscreens act by absorbing ultraviolet radiation that activates the agent’s electrons from the passive to an excited state. When returning to the stable condition, energy is emitted as warmth or fluorescent radiation. Physical agents are composed of sizable particles (titanium dioxide and zinc oxide) that reflect and scatter ultraviolet and visible radiation from a film of inert metal particles which forms an opaque barrier. The disadvantage of physical sunscreens is that lend a “bleached” to the skin, which is scarcely accepted cosmetically and also the tan is not uniform. This is avoided by introducing nanoparticles (single particles with a diameter <100nm) that do not make the skin white and pasty upon topical application, while maintaining the reflective effect and making them look transparent.These measures are necessary for prolonged outdoor activity and particularly important for individuals with light