Researchers have identified for the first time the mechanism by which chronic stress causes hair colour loss, an advance that may lead to the development of novel drugs which can prevent the whitening of hair.
In the study, published in the journal Nature, the scientists induced intense pain in special black mice for several weeks using a substance called resiniferatoxin, and turned the animals’ fur completely white.
“For the longest time it’s been said that stress makes the hair turn white but until now there was no scientific basis for this belief. Our study proved that the phenomenon does indeed occur, and we identified the mechanisms involved,” said Thiago Mattar Cunha from Harvard University in the US.
“In addition, we discovered a way of interrupting the process of hair colour loss due to stress,” Cunha said.
The researchers said resiniferatoxin, which activated sensory nerve fibres, is a naturally occurring chemical found in resin spurge (Euphorbia resinifera) — a cactus-like plant native to Morocco.
According to the scientists, the sympathetic nervous system, which triggers the body’s rapid involuntary response to dangerous situations, is affected directly by the stress, and consists of nerves that branch from the spine and run throughout the body.
It controls the organism’s “fight or flight” response to sudden danger, launching a flash flood of the hormones adrenaline and cortisol to make the heart beat faster, blood pressure rise, respiration accelerate and the pupils dilate, among other systemic effects, they added.
The researchers observed that when the sympathetic nervous system was blocked, hair whitening was curbed.
“After injecting resiniferatoxin into the mice, we treated them with guanethidine, an anti-hypertensive capable of inhibiting neurotransmission via sympathetic fibers. We observed that the process of fur colour loss was blocked by the treatment,” Cunha said.
In another experiment, in which the researchers surgically removed the sympathetic fibres, fur colour was again retained in the weeks following pain induction.