By Heather Brown

MINNEAPOLIS (WCCO) — A survey out of JAMA Dermatology found many people don’t understand the information on sunscreen labels – like what SPF means, what the sunscreen protects people against and how much sunscreen people should use.

So, what do we need to know about sunscreen? Good Question.

READ MORE: Crash Closes Highway 14 In Both Directions Near Owatonna

SPF stands for sun protection factor and it measures the sunscreen’s ability to filter U-VB rays.

“That’s a laboratory value that measures protection by ultraviolet B light,” Dr. Jamie Davis, a dermatologist with Uptown Dermatology, said.

What’s important to understand is SPF doesn’t measure UV-A rays or tell people anything about UV-A protection.

Davis says UV-A and UV-B lights both cause skin cancer.  UV-A goes deeper into the skin, tends to break down collagen and causes wrinkles.  UV-B rays don’t go as deep.

“A tends not to burn,” Davis said. “B tends to burn.”

READ MORE: 1 Of 5 Men Injured In Minneapolis Shooting Dies

Some sunscreens only offer protection against UV-B rays, so Dr. Davis says always look for the words “broad spectrum” on the label. That gives protection against UV-A and UV-B.  She also recommends using a sunscreen with zinc or titanium because those physically, instead of chemically, block the rays.

The SPF numbers tell people how long they can be in the sun before they burn. For example, if you burn after one minute, putting on SPF 15 will protect someone for 15 minutes.  SPF 30 will protect for 30 minutes.

SPF 15 sunscreen also blocks 93 percent of UVB radiation, while SPF 30 sunscreen blocks 97 percent and SPF 50 is closer to 98 percent.

Dr. Davis recommends SPF 50 to people very sensitive to the sun or people with a history of skin cancer, but she recommends SPF 30 or above to her other patients.

“There’s an incremental increase in price,” she said. “And, honestly, 30 does great if you reapply it.”

When it comes to reapplying, Dr. Davis says it’s a must because we sweat, swim and the sunscreen rubs against our clothes.  She also says people don’t wear enough to protect themselves.

MORE NEWS: Colin Powell Dies Of COVID Complications At 84 (CBS News)

“A shot glass full should be enough for the whole body,” she said.

Heather Brown