Next time you find a stray grey hair, don't panic - it's not necessarily the end of the world.
Scientists have discovered it's possible to return hairs that have gone grey back to their original colour, at least for a short while. No, not through dye - but chilling out.
"There is a window of opportunity during which greying is probably much more reversible than had been thought for a long time," Ralf Paus, dermatologist at the University of Miami, told Scientific American.
Dr Paus and colleagues found a number of people with multi-coloured strands of hair - which had started growing their natural shade, before turning grey for some reason.
Based on the rate of growth, they were able to link the changes to real-life events in each person's recent lifetimes they were stressed. In most cases, the hair reverted to growing its original colour when the stress ended.
In one case, a 35-year-old man's greying hair temporarily reverted to its original colour during a two-week vacation. In another, a woman temporarily grew grey hair whilst undergoing a separation and moving house - it went back to normal once it was all over.
"Given the low statistical probability that these events are related by chance, life stress is the likely preceding cause of [this] greying and reversal dynamics," the study, published in journal eLife this week, said.
"It's pretty clear that the hair encodes part of your biological history in some way," said Columbia University mitochondrial psychobiologist Martin Picard, study co-author.
"Maybe there's something to learn there. Maybe the hairs that turn white first are the more vulnerable or least resilient."
But any reversal is likely to be only temporary, the researchers found.
"There might be a threshold for temporary greying; if hairs are about to go grey anyway, a stressful event might trigger that change earlier. And when the stressful event ends, if a hair is just above the threshold, then it could revert back to dark."
But once you're old enough, it's all over - it's time to rock the silver look or start dyeing it.
