Human skin can see ultraviolet light from the sun with sensors scientists previously only found in eyes, according new research. The sensors pick up harmful UV rays and release a chemical that tells the skin it's time to release melanin, they body's natural sunscreen.
The study results may help the pharmaceutical industry develop better sunscreens since sunscreens marketed as broad spectrum may actually block some light that triggers the body's natural defense against harmful UV rays.
The new light receptors in the skin respond within seconds of sun exposure and produce melatonin pigment two hours later, much faster than the days-long exposure times scientists previously thought it took for skin cells to produce the tan-associated pigment.
There was no prior evidence that those receptors can function in skin, Elena Oancea, cell biologist at Brown University, Providence, R.I. and lead author, said. Oancea and her colleagues published their study Thursday in Current Biology.
Oancea had a hunch that skin could see since like eyes, the body's largest organ exposed to light. Researchers in her lab exposed human skin to light of different wavelengths and tracked the response. The light receptors newly identified in skin, called rhodopsin, became most active under blue and UV light.
The results make sense, Oancea said, because the body has to be able to mount a defense against radiation. Melanin blocks the type of UV radiation that causes skin cancer. Another type of UV radiation is primarily responsible for signaling the skin to release melanin. Full sun screen blockage is not necessarily good in man-made sunscreens because the creams and sprays block certain wavelengths of light needed to trigger natural defenses, Oancea said.
Oancea plans to continue researching how the skin's natural light sensors work.
This is just the tip of the iceberg, because there are many things we still need to figure out at the molecular level, she said.