Washington: When it comes to using sunscreens to protect your skin from harmful UV rays while out in the sun and if you're not in the habit of re-applying it every two hours, then it would be better if you didn’t waste your money buying the cream in the first place, a new study shows.
The study was conducted by a group of researchers at the University of California at Riverside led by Kerry Hanson.
As a part of the study, Hanson and her colleagues exposed human skin samples grown in the lab to UV radiation while they were covered with three common UV filters found in sunscreens: benzophenone-3, octocrylene and octylmethoxycinnamate.
They found that after only an hour each compound had sunk into the skin, meaning its protective effect was greatly reduced.
The researchers also found that the samples contained more reactive oxygen species - free radicals that can damage skin cells and increase the risk of skin cancer - than skin exposed to UV with no sunscreen on it.
Hanson said that their findings support the recommendation of the Skin Cancer Foundation in New York that people go no more than two hours between reapplications of sunscreen.
They also state that it might actually be necessary to reapply even more often, and that one way of counteracting free radicals might be to add antioxidants such as vitamins C and E to sunscreens that can help to neutralise reactive oxygen species in the skin.