Did you know that if applied incorrectly, an SPF 30 sunscreen is actually SPF 20?
SPF 30 sunscreen may provide significantly less protection when not enough is used. To get the most out of your sunscreen, use one ounce, enough to fill a shot glass (or your palm). This is the amount needed to cover the exposed areas of the body (arms, legs, neck and face of the average adult) properly. So stock up, use it liberally and reapply often (especially after you towel off).