while it is true that you don’t double your protection when you double the spf number you do get an added benefit. spf numbers are determined through testing under very controlled environments using an amount of product that no one uses in the real world. by using a higher spf sunscreen and reapplying it every two hours or so you are getting closer a reasonable amount of protection. i see patients every day who used sunscreen and yet they are still suntanned or sun burned which means they were not getting the spf they thought they were.
is it correct that anything over an spf 25 really doesn't decrease uva and uvb sun exposure? . i have heard that it "may" add only 2% more protection but the costs of a higher spf is not worth the price point.