A Defense Against UV Radiation
Posted on | October 13, 2009 | Comments Off
To defense against Ultraviolet (UV) radiation, our skin is darkening its color (known as sun tan). Sun Tan works increasing the brown pigment melanin in the skin when exposed to moderate level of radiation (depend on skin type). The purpose of melanin is to absorb ultraviolet (UV) radiation and dissipate the energy as harmless heat, blocking the ultraviolet (UV) from damaging skin tissue. Ultraviolet A (UVA) gives a quick tan that lasts for days by oxidizing melanin that was already present and triggers the release of the melanin from melanocytes. Ultraviolet B (UVB) yields a tan that takes roughly 2 days to develop because it stimulates the body to produce more melanin.
Sunscreen in old days cannot dissipate the energy of the excited state as efficiently as melanin and therefore the penetration of these sunscreen ingredients into the lower layers of the skin may increase the amount of free radicals and reactive oxygen species (ROS). In recent years, improved filtering substances have come into use in commercial sunscreen lotions that don’t significantly degrade or lose their capacity to protect the skin as the exposure time increases (photostable substances).
Sunscreen prevents the direct DNA damage which causes sunburn. Most of these products contain an SPF rating to show how well they block Ultraviolet B (UVB) rays. The SPF rating, however, offers no data about Ultraviolet A (UVA) protection. In the US, the Food and Drug Administration is considering adding a star rating system to show Ultraviolet A (UVA) protection. A similar system is already used in some European countries.
Some sunscreen lotions now include compounds such as titanium dioxide which helps protect against Ultraviolet A (UVA) rays. Other Ultraviolet A (UVA) blocking compounds found in sunscreen include zinc oxide and avobenzone. Cantaloupe extract, rich in the compound superoxide dismutase (SOD), can be bound with gliadin to form glisodin, an orally-effective protectant against Ultraviolet B (UVB) radiation. There are also naturally occurring compounds found in rainforest plants that have been known to protect the skin from ultraviolet (UV) radiation damage, such as the fern Phlebodium aureum.
Tags: actinic keratosis > Skin Cancer Based on Skin Color > Sun Protection > Ultraviolet > Vitamin D > Warning of skin cancer
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