Sun Protection Factors are a benchmark index that measures a sunscreen's ability to protect your skin. You may come across references to 'sun protection index', but nowadays product labels stick to SPF.SPFs are industry standards, meaning that all sunscreen manufacturers use the same index. Numbers such as 15, 30 and 50 refer to the level of protection against UVA and UVB rays. Technically, a sunscreen must be able to provide a level of UVA protection that is at least 1/3 of the number stated. For example, an SPF 30 must guarantee UVA protection that is at least a 10.

But lets get one fact straight: an SPF 50 doesn't stop us from tanning!If you have very pale skin or find it hard to tan, than an SPF 50 is essential. You can then go down to an SPF 30 after a week. Tanning progressively really is the best way! If you've already got a light tan, you can start with an SPF 30, but keep an SPF 50 close to hand. Better safe than sorry - you'll need it if your skin begins to fry.Whatever your case, an SPF 30 is the minimum level of protection if you want to protect your skin and prevent it from ageing prematurely. This goes for both light and dark skins.

No! Even though an SPF 50 effectively protects us from UV rays, it's not a sunblock! Dermatologists agree - even with such a high SPF, we should reapply our sunscreen every couple of hours and immediately after swimming. Some studies say that it's safe to lower your SPF after 4 days.

Sunblocks stopped being used in the UK in 2006. It's an EU law. So what if a sunscreen claims to be a sunblock? Don't believe it!Latest regulations have banned any sunscreen that has an SPF below 6.