“Especially after this study I can tell my friends and relatives, yes, use sunscreen on your kids; I use it on mine,” said lead author Heather Klug, Ph.D., M.P.H., an immunologist and cancer prevention expert from The University of Texas Health Science Center at San Antonio. Dr. Klug is based at the Regional Academic Health Center (RAHC) Medical Research Division, which is the Health Science Center’s campus in Edinburg in the Lower Rio Grande Valley.
Dr. Klug and her colleagues found that mice protected with SPF 15 sunscreen — applied 15 minutes prior to UV light exposure — were several times less likely to develop melanoma than mice coated with lotion that had no SPF (sun protection factor) ingredients. The study is described in the December issue of Pigment Cell & Melanoma Research and in a video online.
“This is the first time that we have been able to prove that a sunscreen will actually prevent a skin cancer, in this case melanoma since we’re using a mouse model that is sensitive to melanoma,” Dr. Klug said in the video.
The research focused on mice with melanocytes (pigment-producing skin cells) that act similarly to human melanocytes. Melanomas, a cancer developing from melanocytes, occurred in 7 percent of the rodents in the control lotion group, compared to only 1 percent in the SPF 15 treatment group. The same area of skin was exposed to UV light in each group.
The scientists applied 2 milligrams of sunscreen per centimeter squared to the skin of 3-day-old mouse pups. “It was a lot of lotion, but it is the amount required by the U.S. Food and Drug Administration for use in determining the SPF rating,” Dr. Klug said. Researchers allowed the sunscreen to soak into the skin for 15 minutes. The animals were then placed under a UV lamp for 15 minutes — equivalent to three hours out in the sun in July, she said.
In addition to reduced occurrence of melanomas, the scientists found less evidence of DNA damage in the SPF 15-protected animals.
The American Academy of Dermatology currently recommends use of sunscreen that is SPF 30 or more. In general, people should use a large amount and wait 15-30 minutes before exposure to the sun. Reapply it often during the day. “I hope people use this information as part of a comprehensive strategy to protect themselves from skin cancer, from melanoma, in the long run,” Dr. Klug said.