Going gray may not just be a badge of age—it may also be a sign that your body has eliminated potentially cancerous cells, according to recent research.
A study from the University of Tokyo using mice has uncovered how hair follicle stem cells respond to DNA damage—and the findings suggest that going gray and developing melanoma may be two divergent outcomes of the same cellular stress.
The 2-Path Response
Researchers focused on pigment-producing stem cells called melanocyte stem cells, which determine whether your hair retains its color or turns gray.
Recently published in Nature Cell Biology, the research used mice to track how these stem cells react to DNA damage. Melanocyte stem cells are found in the hair follicle and can differentiate into mature melanin-forming cells that give hair its color.
When the DNA in these stem cells becomes damaged from X-ray radiation and chemotherapy drugs, the cells respond by not dividing to prevent cancer formation—a process that leads to gray hair.
However, when the DNA damage is caused by ultraviolet light or by carcinogens found in tobacco and car exhaust, these melanocytes would continue dividing and multiplying. In these cases, hair still retained its color, but the animals had a higher risk of melanoma.
In other words, when hair turns gray, it may signal that the body has also avoided melanoma.
These pigment-producing stem cells can either become depleted, which leads to hair graying, or multiply, depending on the kind of stress and signals in their environment, study author Emi Nishimura, a professor at the University of Tokyo, noted in a statement.
When Protection Fails
When exposed to certain cancer-causing agents, such as ultraviolet B light or chemicals such as 7,12-dimethylbenz(a)anthracene—found in tobacco smoke and car exhaust—melanocyte stem cells may bypass their protective process.
Instead, they continue to self-renew and even expand.
However, the fact that you have gray hair doesn’t mean that your body has secretly fought off melanoma. Other processes can also lead to gray hair—including vitamin B12 deficiency, thyroid conditions, and emotional stress.
The study findings help explain why preventing or reversing gray hair could theoretically increase melanoma risk—by interfering with the body’s natural mechanism for eliminating damaged cells.
“It reframes hair graying and melanoma not as unrelated events, but as divergent outcomes of stem cell stress responses,” Nishimura said.
What This Means
Dr. Hannah Kopelman, a dermatologist at Kopelman Aesthetic who was not involved in the study, called the research “really interesting.”
She said it suggests that when pigment stem cells become damaged, they may stop producing color as a kind of self-protection mechanism, which could lower the chance of those cells becoming cancerous.
“It’s a fascinating concept,” Kopelman said. “But I would be cautious about applying it directly to humans.”
She noted that while graying hair doesn’t necessarily mean that a person has reduced skin cancer risk, the findings offer new insight into how aging, pigmentation, and cancer biology may be more closely connected than we once thought.
