Ouch, she should have used more sunscreen: Courtesy Wikipedia

Have you ever been sunburned? Did you wear sunscreen? A recent study published in New Scientist might change your mind on how frequently an individual should reapply sunscreen.

Researchers at the University of California Riverside stated, “if you apply sunscreen anything less than once every two hours, you might be better off not using any in the first place.”

Kerry Hanson and colleagues exposed human skin samples grown in a lab to UV radiation. The samples were covered with three common UV filters found in many sunscreens (benzophenone-3, octocrylene and octylmethoxycinnamate). Findings suggested the protective compounds sunk into the skin resulting in its protective capability being greatly reduced.

Researchers also found the skin samples tested contained more reactive oxygen species (ROS) when compared to skin exposed to UV without sunscreen application. ROS are free radicals that damage skin cells and increase the odds of skin cancer. At low levels, ROS are able to assist in cell signaling processes. However, at higher levels ROS damage cellular macromolecules and could lead to apoptosis (programmed cell death).

For now the researchers advise to use sunscreens and reapply them often. The Skin Cancer Foundation recommends reapplying sunscreen every two hours. Active individuals are advised to reapply even more frequently due to sweat washing away sunscreen.