Green Light May Reduce Pain

UA researcher holds contact lens that allows green light through for rats in pain study.

University of Arizona researchers found that exposure to green light may help reduce pain. Dr. Mohab Ibrahim, director of the Comprehensive Pain Management Clinic at Banner-University Medical Center South, and UA researcher had gotten a call from his brother Wael complaining of a headache.

Dr. Ibrahim told him to take some ibuprofen. Wael countered saying, “No I will just sit among the trees
and that will make me feel better,” Dr. Ibrahim recalled. “It didn’t occur to me until recently that Wael’s headaches were getting better when he just sat among the trees,” said Ibrahim who also serves as assistant professor of anesthesiology and pharmacology at the University of Arizona.

Dr. Ibrahim speculated that maybe it was the quiet and that helped, but he remembered that his own headaches were not relieved in his quiet office. Then, he thought that maybe it was the trees, and perhaps it was something that the trees released in the air, or maybe it was just their color green that is associated with most trees. If it were the color green, he decided, that would be easy to test.

Experiment in Rats

He devised an experiment that exposed rats to green light. One group of rats was exposed to the light from green LED strips affixed to a clear plastic container. Another group was exposed to the room’s white light and fitted with contact lenses that specifically allowed the green spectrum wavelength light to pass through. Then, a third group was fitted with opaque contact lenses that did not allow any of the green light into their visual system.

The rats with the opaque contact lenses did not benefit from the green light exposure.  Ibrahim and his research team published a paper about the study in the journal Pain.

The study found that rats with neuropathic pain that were bathed in green LED demonstrated greater tolerance for uncomfortable tactile and thermal stimuli than rats that were not immersed in green light from LEDs. Also, the team observed no side effects of the therapy nor any sign of visual or motor performance impairment.

The effects of green light exposure are apparent in rats, but how it works remains somewhat of a mystery. Rajesh Khanna, UA associate professor of pharmacology and senior author of the study, noted, “Early studies show that green light is increasing the levels of circulating endogenous opioids, which may explain the pain-relieving effects. Whether this will be observed in humans is not yet known and needs further work.”

Small, Double-Blind Human Trial

So, the team decided to conduct a small, double-blind study of green light exposure on people suffering from the pain of fibromyalgia. Those in the treatment group got a green LED light strip to use in a dark room two hours per day for ten weeks.

The results look promising. Remarkably, two participants even refused to return the green LED light because their pain significantly diminished. Another patient wrote to Ibrahim about how positive the experience was and asked for the light back. Ibrahim obliged.

Also, they found the same results in men and women, despite the fact that some medications to relieve pain work best in people of one gender.

While the results are preliminary, the promise of an inexpensive pain reduction method is greatly needed for those suffering from chronic pain. The team hopes that at least the green light therapy could be used by itself or with other measures to reduce pain, especially for chronic pain sufferers.


Ibrahim, M. M.; Patwardhan, A.; Gilbraith, K. B.; et al… “Long lasting antinociceptive effects of green light in acute and chronic pain in rats,” Pain158(2):347-360, February 2017. doi: 10.1097/j.pain.0000000000000767.

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