INTRODUCTION
Sunlight is critical for the maintenance of life on Earth; however, the ultraviolet (UV) wavelengths (100 nm - 400 nm) associated with sunlight can induce adverse reactions in human skin. The strong intensity ultraviolet C (UVC) (100 nm - 280 nm) is mostly blocked by the ozone layer of the Earth's atmosphere, while UVB radiation (280 nm - 320 nm) and UVA radiation (320 nm - 400 nm) reach the Earth's surface and ultimately the skin.1-3 Ultraviolet B (UVB) radiation is absorbed in the epidermis, the uppermost layer of the skin, causing sunburn and DNA damage, such as thymine dimer formation. On the other hand, longer wavelength UVA radiation penetrates the skin deeper and into the dermis, causing harm through oxidation.4
The American Academy of Dermatology (AAD) recommends that everyone should use a sunscreen product on a daily basis when they are outdoors. They should choose products that offer broad-spectrum protection, ie, protect against UVA and UVB radiation, with a sun protection factor (SPF) 30 or greater.5 In a consumer survey of attitudes and habits toward sunscreens, almost half of the participants indicated that the SPF factor was the top factor in their buying decision -- which unfortunately misses the benefits of UVA protection. By contrast, having a "broad-spectrum sunscreen" was only the fifth-highest factor, and garnered support from only one-third of consumers,6 suggesting that consumer education on sun protection is still needed.
The American Academy of Dermatology (AAD) recommends that everyone should use a sunscreen product on a daily basis when they are outdoors. They should choose products that offer broad-spectrum protection, ie, protect against UVA and UVB radiation, with a sun protection factor (SPF) 30 or greater.5 In a consumer survey of attitudes and habits toward sunscreens, almost half of the participants indicated that the SPF factor was the top factor in their buying decision -- which unfortunately misses the benefits of UVA protection. By contrast, having a "broad-spectrum sunscreen" was only the fifth-highest factor, and garnered support from only one-third of consumers,6 suggesting that consumer education on sun protection is still needed.
Skin damage from UV radiation can take many different shapes and forms, such as erythema, photoaging, DNA damage, and carcinogenesis, among others.7 In fact, UV radiation is classified as a Group I carcinogen (in the same category as arsenic and asbestos) by the World Health Organization.8 An exposure of the skin to UV radiation can increase inflammatory cytokines, such as interleukin-1alpha.9 UVB irradiation can also lead to the formation of thymine dimers,10 which may ultimately lead to skin cancer, in the absence of repair.11 Sub-lethal doses of UV radiation decrease cell proliferation -- likely to allow cellular systems to check for damage incurred and correct mutations.12
