What does the UV Index mean?
The UV index tells you how strong the sun’s UV rays will be; the higher the UV index, the greater the strength of the sun’s UV rays and the more likely you will burn.
The Met Office forecast uses the UV index to warn you of an increased risk to health from UK radiation. The ‘Solar UV Index’ was developed by the World Health Organization. The Met Office UV forecasts include the effects of:
- the position of the sun in the sky
- forecast cloud cover
- ozone amounts in the stratosphere
What does SPF mean?
SPF or Sun Protection Factor is worked out under lab conditions to give an indication of how much protection a sun cream can offer.
The following equation is used:
Minutes to burn without sunscreen x SPF number = maximum sun exposure time
So if you would burn without sun protection in 10 minutes and you applied a factor 30 protection, you could theoretically be protected for up to 300 minutes.
BUT, it’s important to remember that lots of factors can affect how long your sun cream will protect you for. Sweating, swimming, clothes rubbing on your skin, your skin type and strength of the sun will all reduce your protection.
It’s also important to remember that lab tests are different to real world use; most users won’t apply sun cream as liberally or regularly as scientist will for these tests.
What’s the difference between SPF 30 and SPF 50?
Interestingly, SPF50 offers only marginally better protection from UV radiation than SPF30 filtering out 98 per cent of UV radiation compared to 96.7 per cent blocked by SPF30.
Using SPF50 is not a substitute for applying suncream less frequently. SPF50 sunscreen still needs to be applied as liberally, re-applied every two hours (or after swimming, exercising and towel drying) and used in combination with other sun protection measures including sun protective hats, protective clothing, sunglasses and shade.