While 80 percent of Americans know they should apply sunscreen every two hours when outdoors, few do it.

Your patients likely need a refresher course on sunscreen application and SPF. This is the main takeaway message of a recent survey of 1,000 U.S. adults by the American Academy of Dermatology.

While 80 percent of Americans know they should apply sunscreen every two hours when outdoors, few do it, the survey showed. Moreover, only 33 percent typically reapply sunscreen every two hours, while 42 percent either tend to not reapply sunscreen at all or reapply it only when they get wet. Fully 30 percent apply sunscreen just to their face instead of also applying it to other areas of their body, the survey found.

“As family and friends get together outdoors this holiday weekend and throughout the summer, we want to remind everyone to practice safe sun, which includes seeking shade, wearing sun-protective clothing, and applying sunscreen every two hours when outdoors, or after swimming or sweating, to all skin not protected by clothing,” says dermatologist Henry W. Lim, MD, FAAD, former chair of the department of dermatology at Henry Ford Hospital in Detroit, in a news release.

“Reapplication is key along with understanding SPF. Many people mistakenly assume that they can apply the sunscreen with the highest SPF rating and then stay out in the sun all day without reapplying; however, SPF is a measurement of how well a sunscreen protects the skin from the sun’s UVB rays, which cause sunburn. It is not a measurement of how long someone can stay in the sun or how frequently it needs to be applied.”

Alongside seeking shade and wearing sun-protective clothing, Dr. Lim says sunscreen is a vital tool in the fight against skin cancer. Research suggests that daily use of sunscreen reduces the risk of melanoma, the deadliest form of skin cancer. However, sunscreen labels can be confusing for even the most sun-savvy consumers, says Dr. Lim.

A recent report in JAMA Dermatology found that when it comes to selecting sunscreen, most consumers consider the Sun Protection Factor (SPF) rating to be the most important criteria.

“There is a lot of information on sunscreen labels, and one piece of information isn’t necessarily more important than another,” says Dr. Lim. “I tell my patients to look for three things when choosing a sunscreen — SPF 30 or higher, broad-spectrum protection, and water resistance.”

In recognition of Skin Cancer Awareness Month in May, the AAD is encouraging Americans to #PracticeSafeSun to protect themselves and their families from skin cancer.