This is a common topic of confusion. SPF stands for Sun Protection Factor. This factor is a measure of how much ultraviolet (or UV) radiation it takes to burn your skin when it’s unprotected compared to how much it takes to burn it when it’s slathered in sunscreen. The higher the SPF value of your sunscreen, the more protection it offers from sunburn. It is important to note that sunscreens with higher SPF do not last or remain effective on the skin any longer than lower SPF and must be continually reapplied as directed, usually every two hours.
There is only a 1% increased UV protection from using factor 50 over factor 30. In fact, even factor 15 gives over 90% protection (based on a relative scale). Those who apply SPF 50 can have a false sense of security and assume they will manage much longer in the sun before burning. Bear in mind, that damage is occurring before you hit the sunburn threshold. Applying an effective SPF cream is about damage limitation. The key is to ensure a physical sunscreen agent is in the product and also to reapply every 2 hours if in the sun. (This would include when sitting behind a glass window in an office or car when the sun is strong, or you are very sensitive to the sun’s rays). There are obviously other factors to consider e.g. time of year, time of day, geographical location etc.
The SPF is an imperfect measure of skin damage because invisible damage and skin ageing are also caused by ultraviolet type A (UVA), which does not primarily cause reddening or pain. Conventional sunscreen blocks very little UVA radiation relative to the nominal SPF; broad-spectrum sunscreens are designed to protect against both UVB and UVA. According to a 2004 study, UVA also causes DNA damage to cells deep within the skin, increasing the risk of malignant melanomas. Even some products labelled “broad-spectrum UVA/UVB protection” have not always provided good protection against UVA rays. Our FDA-approved morning cream has proven broad-spectrum UVA and UVB protection with 2 of the most superior active sunscreen ingredients known. The choice of product in our clinic is not based on SPF number, but on your skin type and need. All range from 30-50 and as mentioned above, this should not be the deciding factor. One of our skincare specialists will be able to advise you on the best product for you.