People spend a lot of money to dye the grays away – analysts estimate 29 billion will be spent worldwide by 2019. However, an unexpected side effect of a cancer treatment might help scientists develop a new method of restoring hair color without dyes. Researchers in Spain found that patients undergoing immunotherapy treatment for lung cancer also experienced hair darkening, reports The Guardian.

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Scientists at the University of Barcelona studied the effects of the drugs on 52 patients with lung cancer and found that 13 people’s hair changed to dark brown or black. In one white-haired patient, the treatment caused black patches. Published in medical journal JAMA Dermatology, the team notes in the paper that most of the patients responded very well to treatment – only one had to stop as the cancer progressed.

“It’s a fascinating report – one of those things that comes out of the blue,” June Robinson, dermatology professor at Northwestern University and editor of JAMA Dermatology, told The Guardian.

Despite the promising find, this study was very small and it’s way too soon to bank on immunotherapy drugs for their anti-aging benefits. Noelia Rivera, a dermatologist at Autonomous University of Barcelona, told the paper that the medications have very serious side effects that make them unsuitable for healthy people. But doctors could use this research to develop a different treatment for gray hair. Prior research has shown that these treatments can cause gray hair in melanoma patients, so there's a lot more that needs to be determined.

While radiation and chemotherapy are more commonly known, there’s been lots of excitement over using immunotherapy to target cancer in recent years. Dubbed a “promising new frontier in the war on cancer,” research for the method actually began more than 100 years ago, according to the Memorial Sloan Kettering Cancer Center. The practice essentially uses the body’s immune system to fight off diseases.

Dr. William Coley, known as the pioneer of immunotherapy, began researching cancer treatments after losing an 18-year-old patient to sarcoma. Coley discovered the case of a 31-year-old New Yorker whose cancer was cured after coming down with a skin infection caused by strep bacteria, recounts the cancer center.

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After discovering more and more cases of cancers seemingly cured by infections, the doctor began his own experiments and injected bacterias into patients with cancerous tumors. In the late 1800s and early 1900s, little was known about the immune system and Coley’s method fell by the wayside as chemotherapy and radiation treatments emerged.

Dr. Steven Rosenberg, M.D., PhD and researcher at the National Cancer Institute, has been researching immunotherapy for four decades, reports CBS. He told the outlet that despite its long history, there’s still a lot more to uncover. "We've gotten to the point now where I think we understand why the patients who are successfully treated experience tumor regression," Dr. Rosenberg said. "And based on that knowledge, I think we're going to see dramatic progress in the next few years to come."

Outside of cancer treatments, scientists are finding new ways to use immunotherapy (beyond a possible cure for gray hair). A study from last year indicated that injections of an HIV antibody could functionally cure the disease, meaning the virus exists in very small amounts, symptoms would be virtually nonexistent and virus replication would be stopped. The research is still in its infancy and researchers acknowledge they are years away from making this a fully working treatment in humans.

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