According to the American Academy of Pain Medicine, approximately 100 million people in the US alone suffer from chronic pain. Although opioids (powerful pain relievers) may help, they can cause serious side effects such as dizziness, vomiting and constipation – plus they're addictive. So, what alternatives are there? Well, new research from the University of Arizona indicates that exposure to green light may be another way to go.

Led by Drs. Mohab Ibrahim and Rajesh Khanna, a UA team studied three groups of rats, all of which suffered from neuropathic pain.

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One group was placed in clear plastic containers illuminated solely by strips of green LEDs – the lights were on for eight hours a day, over a period of five days. Another group, although lit by regular room light, were fitted with contact lenses (pictured below) that allowed only the green spectrum to get through to their eyes. The third group wore opaque contacts, that didn't let them see light of any color.

When the animals were subsequently tested, the first two groups exhibited significantly more tolerance for tactile stimulus than the control group. The pain-relieving effect lasted for four days after the light exposure, with no side effects being noted.

Although the reasons for the reaction aren't entirely understood, the scientists believe that it may be because the green light boosts levels of natural opioids circulating within the rats' bodies. Whether or not that effect occurs in humans is another question, which is why a 10-week clinical trial is now being conducted on people with fibromyalgia. Dr. Ibrahim tells us that the results so far are encouraging.

As an interesting side note, a 2016 Harvard study indicated that green light also helps alleviate migraine headaches – again, the reason why wasn't immediately clear.

A paper on the UA research was recently published in the journal Pain.

Source: University of Arizona

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