Low vitamin D status (sometimes called vitamin D deficiency) is defined by the Department of Health as a plasma concentration of 25 hydroxyvitamin D (the main circulating form of the vitamin) of below 25 nmol/litre (equal to 10 ng/ml).
Photoageing results from chronic exposure to UV radiation. It may include any or all of the following: dryness, itching, wrinkling, irregular pigmentation, sallowness, irregular blood vessel dilatation, enlarged blackheads, fragility with easy bruising and loss of skin elasticity.
Any covering clothing with close‑weave fabrics that do not allow sunlight through.
Six different skin types have been identified:
Type I: Often burns, rarely tans. Tends to have freckles, red or fair hair, blue or green eyes.
Type II: Usually burns, sometimes tans. Tends to have light hair, blue or brown eyes.
Type III: Sometimes burns, usually tans. Tends to have brown hair and eyes.
Type IV: Rarely burns, often tans. Tends to have dark brown eyes and hair.
Type V: Naturally brown skin. Often has dark brown eyes and hair.
Type VI: Naturally black‑brown skin. Usually has black‑brown eyes and hair.
Further information on determining skin type was completed by the Health Protection Agency and is available from Cancer Research UK (www.cruk.org/sun).
Sunburn is pink or red skin caused by sunlight exposure. Sunburn is an indicator of skin damage. For those with naturally dark skin, damage may be indicated by their skin getting hot in the sun and then staying hot afterwards, rather than signs of redness. Note: it is not necessary for the skin to burn to get skin damage and a suntan offers little protection against further skin damage. Furthermore, getting a suntan increases the risk of skin cancer.
The UV index indicates how strong the sun's UV rays are and when there may be an increased risk of burning. UV index forecasts for different parts of the UK are available from the Met Office (www.metoffice.gov.uk), or by looking at many weather forecasts.