UV rays only account for 5% of the sun rays that reach the earth, but they are very powerful. There are several kinds. While UVC rays are blocked by the ozone layer, UVA and UVB rays reach the earth and have an effect on the skin.
UVA: A as in "ageing" or "allergies"
Occurring throughout the year and even on cloudy days, UVA's account for 95% of the ultraviolet rays that touch the earth's surface. They pass through clouds, glass and the epidermis; unlike UVB's, they are painless and can penetrate very deeply into the skin to reach the cells of the dermis. As they primary produce free radicals, they can alter cells in the long term and bring about:
- Photoageing: A change in the orientation of elastin and collagen fibres, causing skin to slacken and lose its firmness and wrinkles to appear
- Sun intolerance, commonly referred to as sun allergies (redness, itching, summer light eruption)
- Pigmentation disorders (pregnancy mask, spots)
- Development of skin cancers.
UVB: B as in "burns" or "bronzed skin"
UVB rays constitute 5% of the ultraviolet radiation received on the earth. They are very high in energy and are stopped by clouds and glass; they can penetrate the epidermis. They are responsible for tanning, but also burns (sunburns), allergic reactions and skin cancers. It is therefore important to protect the skin from both UVA and UVB rays.