Vivian Gerson, 4, and her mom Laura just learned there's a sure-fire sunscreen application technique.
"The guide really does help. It really does help you understand what you might be missing," said Laura.
Laura thought she was being thorough, but without precise guidance it's guesswork.
Even though you bought sunscreen with a sun-protection factor (SPF) of 30, your might just be applying an SPF of 10.
"And you get wide variability among different people in terms of how much sunscreen they're actually putting on," said pediatric dermatologist Dr. Robin Schaffran.
Schaffran created an 11-zone guide based on scientific research done in the lab.
Each zone of Vivian's body represents 9 percent of her skin's body area. The correct dose is 2 milligrams per centimeter. So how do you know if you're getting the right dose? Doctors have a trick.
Squeeze a strip of sunscreen on the middle and pointer finger from the base to the tip.
"You would use the child's fingers to measure it. So it's not your fingers to measure the child. The dose is based on the person who is putting it on," said Schaffran.
And apply every two hours. Since the proper dosage is more than most parents apply, Schaffran recommends using sunscreens that use mineral-based protection using ingredients like titanium dioxide and zinc oxide.
"I like to advise parents to try doing this exercise at least once, so you get a sense of exactly how much sunscreen you're supposed to be putting on," said Schaffran.