Few harbingers of onetime age are clearer than the sight of gray pilus. As we grow older, black, brown, blonde or red strands lose their youthful hue. Although this may seem similar 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 instance studies within the scientific literature for decades. In one 1972 paper, the late dermatologist Stanley Comaish reported an come across with a 38-year-old man who had what he described as a "most unusual feature." Although the vast majority of the individual'southward hairs were either all black or all white, three strands were calorie-free near the ends but dark most the roots. This signaled a reversal in the normal graying procedure, which begins at the root.

In a study published today in eLife, a group of researchers provide the most robust evidence of this miracle to date in hair from around a dozen people of various ages, ethnicities and sexes. Information technology also aligns patterns of graying and reversal to periods of stress, which implies that this crumbling-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 reversible than had been idea for a long time," says study co-writer Ralf Paus, a dermatologist at the Academy of Miami.

Effectually iv years ago Martin Picard, a mitochondrial psychobiologist at Columbia Academy, was pondering the way our cells grow old in a multistep manner in which some of them begin to evidence signs of aging at much earlier time points than others. This patchwork procedure, he realized, was conspicuously visible on our head, where our hairs do not all turn gray at the same fourth dimension. "Information technology seemed like the hair, in a way, recapitulated what nosotros know happens at the cellular level," Picard says. "Peradventure in that location's something to learn there. Perhaps the hairs that turn white commencement are the more vulnerable or least resilient."

While discussing these ideas with his partner, Picard mentioned something in passing: if i could find a hair that was only partially greyness—and and so summate how fast that pilus was growing—it might be possible to pinpoint the flow in which the hair began crumbling and thus ask the question of what happened in the individual's life to trigger this modify. "I was thinking well-nigh this almost as a fictive thought," Picard recalls. Unexpectedly, however, his partner turned to him and said she had seen such 2-colored hairs on her head. "She went to the bathroom and actually plucked a couple—that's when this projection started," he says.

Picard and his team began searching for others with two-colored hairs through local ads, on social media and by discussion of oral fissure. Somewhen, they were able to discover 14 people—men and women ranging from ix to 65 years former with various indigenous backgrounds (although the majority were white). Those individuals provided both single- and two-colored hair strands from dissimilar parts of the torso, including the scalp, face and pubic surface area.

The researchers and then adult 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 likewise found that this occurred non just on the caput but in other bodily regions likewise. "When we saw this in pubic hair, nosotros thought, 'Okay, this is existent,'" Picard says. "This happens not just in one person or on the head merely across the whole body." He adds that because the reversibility only appeared in some hair follicles, however, information technology is likely limited to specific periods when changes are nevertheless able to occur.

Well-nigh people offset noticing their first gray hairs in their 30s—although some may find them in their late 20s.This menses, when graying has just begun, is probably when the process is most reversible, according to Paus. In those with a total head of greyness hair, nigh of the strands have presumably reached a "betoken of no return," only the possibility remains that some hair follicles may nevertheless be malleable to modify, he says.

"What was virtually remarkable was the fact that they were able to show convincingly that, at the individual hair level, graying is actually reversible," says Matt Kaeberlein, a biogerontologist at the Academy of Washington, who was ane of the editors of the new paper but was not involved in the work. "What nosotros're learning is that, not but in hair but in a variety of tissues, the biological changes that happen with historic period are, in many cases, reversible—this is a squeamish example of that."

The team also investigated the association between hair graying and psychological stress because prior research hinted that such factors may advance the hair's aging process. Anecdotes of such a connection are too visible throughout history: co-ordinate 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 pocket-sized subset of participants, the researchers pinpointed segments in single hairs where color changes occurred in the pigmentation patterns. Then they calculated the times when the change happened using the known average growth rate of human being hair: approximately one centimeter per calendar month. These participants as well provided a history of the virtually stressful events they had experienced over the class of a twelvemonth.

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-old human being with auburn hair, 5 strands of hair underwent graying reversal during the same time span, which coincided with a two-calendar week vacation. Another subject area, a 30-yr-former woman with black hair, had ane strand that contained a white segment that corresponded to two months during which she underwent marital separation and relocation—her highest-stress period in the year.

Eva Peters, a psychoneuroimmunologist at the Academy Infirmary of Giessen and Marburg in Germany, who was not involved in this work, says that this is a "very artistic and well-conceptualized report." Only, she adds, considering the number of cases the researchers were able to look at was relatively small—particularly in the stress-related portion of the study—further research is needed to confirm these findings.

For now, the side by side step is to look more carefully at the link betwixt stress and graying. Picard, Paus and their colleagues are currently putting together a grant to conduct 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 call up life events from the past.

Somewhen, Picard says, one could envision hair as a powerful tool to assess the effects of earlier life events on aging—considering, much like the rings of a tree, hair provides a kind of concrete tape of elapsed events. "Information technology's pretty clear that the pilus encodes part of your biological history in some fashion," he says. "Hair grows out of the body, and then information technology crystallizes into this hard, stable [structure] that holds the memory of your past."