Few harbingers of old age are clearer than the sight of gray hair. Every bit nosotros grow older, black, brown, blonde or red strands lose their youthful hue. Although this may seem like a permanent change, new research reveals that the graying process can be undone—at least temporarily.

Hints that gray hairs could spontaneously regain color have existed as isolated case studies inside the scientific literature for decades. In 1 1972 newspaper, the tardily dermatologist Stanley Comaish reported an encounter with a 38-year-one-time man who had what he described as a "nearly unusual feature." Although the vast majority of the individual's hairs were either all black or all white, 3 strands were light virtually the ends only dark well-nigh the roots. This signaled a reversal in the normal graying process, which begins at the root.

In a study published today in eLife, a group of researchers provide the most robust evidence of this phenomenon to appointment in hair from effectually a dozen people of diverse ages, ethnicities and sexes. Information technology also aligns patterns of graying and reversal to periods of stress, which implies that this aging-related process is closely associated with our psychological well-being.

These findings suggest "that there is a window of opportunity during which graying is probably much more than reversible than had been thought for a long time," says report co-writer Ralf Paus, a dermatologist at the Academy of Miami.

Effectually four years agone Martin Picard, a mitochondrial psychobiologist at Columbia University, was pondering the mode our cells abound quondam in a multistep manner in which some of them begin to show signs of crumbling at much earlier time points than others. This patchwork procedure, he realized, was clearly visible on our head, where our hairs practise not all turn gray at the same time. "Information technology seemed like the hair, in a way, recapitulated what we know happens at the cellular level," Picard says. "Maybe there'due south something to learn there. Maybe the hairs that turn white get-go are the more vulnerable or least resilient."

While discussing these ideas with his partner, Picard mentioned something in passing: if 1 could find a hair that was but partially grey—and and so calculate how fast that hair was growing—it might be possible to pinpoint the period in which the hair began crumbling and thus ask the question of what happened in the individual'southward life to trigger this change. "I was thinking about this nigh as a fictive idea," Picard recalls. Unexpectedly, however, his partner turned to him and said she had seen such two-colored hairs on her head. "She went to the bathroom and actually plucked a couple—that'southward when this project started," he says.

Picard and his team began searching for others with two-colored hairs through local ads, on social media and past word of oral cavity. Eventually, they were able to find xiv people—men and women ranging from 9 to 65 years old with various ethnic backgrounds (although the majority were white). Those individuals provided both single- and two-colored hair strands from different parts of the body, including the scalp, face and pubic expanse.

The researchers then developed a technique to digitize and quantify the subtle changes in color, which they dubbed hair pigmentation patterns, along each strand. These patterns revealed something surprising: In 10 of these participants, who were between age nine and 39, some graying hairs regained color. The team besides found that this occurred not just on the head but in other bodily regions as well. "When we saw this in pubic hair, we idea, 'Okay, this is real,'" Picard says. "This happens not just in one person or on the head but across the whole body." He adds that because the reversibility only appeared in some hair follicles, however, it is likely limited to specific periods when changes are all the same able to occur.

Nearly people starting time noticing their first greyness hairs in their 30s—although some may detect them in their late 20s.This period, when graying has only begun, is probably when the process is most reversible, according to Paus. In those with a full head of grayness pilus, most of the strands have presumably reached a "point of no return," but the possibility remains that some hair follicles may even so exist malleable to alter, he says.

"What was almost remarkable was the fact that they were able to show assuredly that, at the individual hair level, graying is actually reversible," says Matt Kaeberlein, a biogerontologist at the University of Washington, who was one of the editors of the new paper but was not involved in the work. "What we're learning is that, not but in hair only in a variety of tissues, the biological changes that happen with age are, in many cases, reversible—this is a dainty instance of that."

The team also investigated the association betwixt hair graying and psychological stress because prior research hinted that such factors may accelerate the hair's crumbling process. Anecdotes of such a connectedness are also visible throughout history: according to legend, the hair of Marie Antoinette, the 18th-century queen of France, turned white overnight just earlier her execution at the guillotine.

In a small subset of participants, the researchers pinpointed segments in unmarried hairs where color changes occurred in the pigmentation patterns. And then they calculated the times when the change happened using the known average growth charge per unit of homo hair: approximately 1 centimeter per calendar month. These participants likewise provided a history of the almost stressful events they had experienced over the course of a year.

This assay revealed that the times when graying or reversal occurred corresponded to periods of significant stress or relaxation. In one individual, a 35-year-quondam homo with auburn hair, 5 strands of hair underwent graying reversal during the same time bridge, which coincided with a two-calendar week vacation. Another subject field, a 30-year-former woman with black pilus, had i strand that independent a white segment that corresponded to ii months during which she underwent marital separation and relocation—her highest-stress period in the year.

Eva Peters, a psychoneuroimmunologist at the Academy Hospital of Giessen and Marburg in Germany, who was not involved in this work, says that this is a "very artistic and well-conceptualized study." But, she adds, because the number of cases the researchers were able to await at was relatively small-scale—particularly in the stress-related portion of the report—farther enquiry is needed to confirm these findings.

For now, the side by side step is to expect more advisedly at the link between stress and graying. Picard, Paus and their colleagues are currently putting together a grant to acquit some other study that would examine changes in hair and stress levels prospectively—which means tracking participants over a specified period of time rather than asking them to recall life events from the past.

Eventually, Picard says, one could envision hair as a powerful tool to assess the furnishings of earlier life events on aging—considering, much like the rings of a tree, pilus provides a kind of physical record of elapsed events. "It'southward pretty clear that the hair encodes part of your biological history in some way," he says. "Hair grows out of the body, and and then it crystallizes into this difficult, stable [structure] that holds the memory of your by."