Premature whitening of hair may be reversed in select cases, say where it happens because of illness or extreme stress. Researchers from Manchester University and Lubeck University, in Germany, used a molecule to stimulate the pigment responsible for hair colour.
But they said the technique still had to be tested on humans and would not reverse the natural greying process. Still it is seen as an an encouraging breakthrough.
The research team recreated a naturally-occurring molecule called K(D)PT, which is very similar to the hormones in the body that stimulate the hair pigment melanin.
The researchers took hair follicles from six women aged between 46 and 65 and mimicked two conditions which can turn hair white - a skin disease known as alopecia areata and stress-related disorder telogen effluvium.
They found that, once treated with K(D)PT, the amount of melanin in the follicle increased significantly.
Lead researcher Dr Ralf Paus said the melanin stimulation suggested the technique could be used as an "anti-greying agent".
Nina Goad, of the British Association of Dermatologists, said: "It's important to note that this is laboratory research and not yet ready for use on patients.
"At the moment, this research only applies to people whose hair has turned white following illness, but this is an important step for such patients."