The answer to this question involves a process known as dry-down time, which basically is the amount of time before the sunscreen no longer feels wet on the skin. When you apply sunscreen, it creates a film on the skin that interacts and mixes with the oil, sebum, and sweat molecules that are already present. This film needs to dry before the sunscreen is “locked on”, thus blocking the sun’s radiation and keeping your skin from being prematurely aged. The very popular sunscreen sprays have the shortest dry-down time (about a minute or so), while sunscreen creams and lotions have the longest (5-10 minutes).
Keep in mind that even though sprays dry the quickest, they have to be rubbed in with your hands to evenly distribute the sunblock. One tip is to hold the spray 4 inches from your skin while spraying and rubbing. This avoids the common mistake of creating an “orb” of sunscreen spray one often sees at pools and the beach, which looks like a cloud of mist around a person. When you create this orb, most of the sunscreen never comes into contact with the skin, rendering it useless against the sun’s age-accelerating rays.
Dana Point Dermatology also does not recommend sprays for use on the face (especially during water sports or workouts) because the ingredients, most commonly oxybenzone or avobenzone, can drip down the face into the eyes and sting.
Dana Point Dermatology’s Bottom Line: The 30-minute rule is a myth; once the sunscreen is dry on your skin, you’re good to go.
