How often should sunscreen be applied?
sunscreens are usually tested for 80 minutes of efficacy.
for example, if a company was making a SPF 15, the SPF would
have to be at or above 15 at minute 1 and minute 81.
most sunscreens should be reapplied every two hours, and it's
about 1oz (a shot) of sunscreen you should be using for your whole
body each application.
have fun in the sun and be safe!