Does an SPF30 sun lotion give twice the protection of an SPF15 product? No – SPF stands for Sun Protection Factor and measures the protection against UVB provided by a sunscreen. An SPF15, when applied properly, protects you against 16 out of 17 parts or 93% of UVB. An SPF 30 protects you against 32 out of 33 parts or 97% UVB.
SPF50 will block 98% of UVB rays and SPF100 99%.
In reality there is actually not much difference between SPF15 and SPF100 – at least a lot less difference than the SPF figure appears to represent. The fact is that, as long as they are properly applied, most sun lotions offer quite a high level of protection and it just isn’t necessary for most of us to use an ultra-high SPF sunscreen.
SPF ratings higher than 30 are primarily used by sun care companies as a marketing tool, and take advantage of the public’s misperception of what the protection ratings mean.
More worryingly is the fact that these higher SPF levels encourage people to spend longer periods in the sun as they are not visibly burning. However, UVA rays will still be getting through, and it is thought that these are far more damaging in the long term than UVB rays. UVA penetrates deeper into the skin where it can affect living cells in the dermis. This damage can cause symptoms of premature ageing such as fine lines and wrinkles, and can also damage the DNA that carries the genetic code of each cell. If the DNA becomes damaged, cells may mutate and this is thought to be a leading cause of skin cancers.
It is far more important to apply sun lotions in sufficient quantity, to reapply regularly, and to wear protective clothing during exposure to strong sunlight, than it is to use sun lotions with very high SPF factors. Applying half the recommended amount of sun lotion will only give protection equal to the square root of the claimed SPF level. This means that applying half the recommended amount of an SPF15 product will only give approximately SPF4 protection, whilst half the amount of SPF30 will only give approximately SPF5½. As you see from these figures, the difference in protection level between these two products is minimal.
An average adult should use about a 30ml or shot-glass-full to cover the entire body. At this level, an SPF15 sun lotion will filter out 93% of UVB rays, whilst and SPF25 will filter out 96% of UVB. You should also reapply every 2 to 3 hours and always after swimming or profuse sweating in order to maintain protection.
NICE (The National Institute for Health and Clinical Excellence) published guidance advising people to use a broad spectrum sun lotion with at least SPF15 protection.
Content kindly provided by Green People