Gary Fisher, Ph.D., and Frank Wang, M.D., led the study on the skin aging effects of UVA1.

Shun the sun

Brief exposure to UVA1 rays starts skin-aging process

issue 21 | Spring-Summer 2014

A low level of daily exposure to a common component of sunlight and tanning bed light can cause skin damage at the molecular level after just a few days, U-M dermatology research shows. The findings highlight the need for better sunscreens to protect against these damaging rays and prevent the process that can cause skin to look old, wrinkled and sagging prematurely.

For physicians, the findings offer more ammunition when counseling patients on sun exposure and tanning bed use.


Writing in JAMA Dermatology, the researchers show that damage starts after just two daily exposures to a low amount of ultraviolet A1, or UVA1, light. UVA1 makes up most of the UV light throughout the day, and tanning bed light, too. The damaging process kept going after further daily exposures.

The researchers measured the effects of UVA1 at the molecular level using advanced gene expression analysis of skin samples from human volunteers. They focused a low level of pure UVA1 rays, as might be encountered in daily life, on small areas of 22 volunteers' buttocks. A day later, they measured changes in skin pigmentation. Then, they took tiny samples of skin, in order to detect which genes had been "turned on" by the light exposure. They repeated this process three more times on each participant.


After just two exposures, UVA1 rays caused skin cells to make molecules that break down collagen, which makes skin firm, smooth and youthful in appearance. UVA1 also caused the skin to darken a little with each exposure, but this tan didn't protect against further production of the collagen-destroying molecule, called matrix metalloproteinase 1, or MMP1, when the skin was exposed to more doses of UVA1.

U-M dermatologist and lead author Frank Wang, M.D., notes that he often observes the collagen-damaging effects of repetitive sun or tanning booth exposure in people in their 20s and 30s who come in for other conditions, but have clear signs of premature aging to their skin.

Very few of the ingredients in sunscreen effectively protect against UVA1. The new findings suggest a need for new sunscreen ingredients that can protect against UVA1 rays, beyond zinc oxide and avobenzone. Window glass and most clothing also don't necessarily filter out all UVA1, which is present whenever it's daytime.

The study was done by a team from the U-M Department of Dermatology's Photobiology and Aging Skin Research Program, led by Gary Fisher, Ph.D.