SunGuard.co.ukWhat is SPF?
SPF stands for sunburn protection factor. This term is used to describe the protection that a sun cream or sun screen can give you when you expose your skin to the sun. The calculations here are based on how much sun exposure it would take to burn the skin with sun cream as opposed to how much it would take to burn the skin without sun cream.
In general terms the SPF given with a sun cream will give higher protection the higher the SPF number is. So, factor 40 will give more protection than factor 15. Levels here start at 1 and go up to around 60. The protection here is not about how long you stay in the sun (so factor 10 won't give you 10 hours of protection!) as this is all about the protection that you'll get from a cream in the first place. So, putting on a factor 40 cream doesn't mean that you can stay out in the sun longer than somebody who is wearing factor 20 - it simply means that you will get higher levels of protection than they do while you are in the sun and while the cream is working.
All sun creams and screens need regular re-applications especially if you are swimming or doing strenuous physical activity. Most products here will recommend re-application every few hours and it is important to follow the instructions that you are given to get the maximum possible protection.
It is also important to think about who you are protecting here and what kind of skin type they have. Kids, for example, need higher protection than many adults and people with fair skin will generally need stronger SPFs than people with darker skin as they burn more easily.