Water-resistant sunscreen lotions containing microscopic sponges are being developed to protect the skin all day against the sun's ultraviolet rays, a California dermatologist said last week.
The tiny sponges also would regulate skin absorption of the lotions, thus minimizing irritations and allergic reactions, Dr. Sergio Nacht said at an American Cancer Society science writers forum in San Diego. He said each sponge is made of porous plastic and measures 0.001 of an inch in diameter.
When the sponge is immersed in a sunscreen formula, its 250,000 tiny pores trap the lotion. Throughout the day, the sunscreen is squeezed out of the sponge's pores in small amounts by normal body movement.
The product may be on the market within a year, according to Nacht, who worked on the technology at Advanced Polymer Systems in Redwood City.
In tests on humans, he said, researchers found that "simply by rubbing (the skin) at various intervals, we can obtain a repeat release of the active (sunscreen) compound. In contrast, a similar preparation containing the active ingredient in a "free" form gradually lost efficacy, thus offering little protection after a few hours, Nacht said.
These microsponges also may be used to combine sunscreens that protect against the sun's intense ultraviolet-B rays, which are linked to sunburn and cancer, with sunscreens that ward off the longer-length ultraviolet-A rays, which are associated with wrinkling and damage to deeper skin layers, he said.