Can plucking hair stimulate more hair to regrow?

Can plucking hair stimulate more hair to regrow?

"Plucking hairs 'can make more grow'," BBC News reports, while the Daily Mail went as far as saying scientists have found "a cure for baldness".

But before you all reach for your tweezers, this discovery was made in mice, not humans!

The study was carried out by researchers from the University of Southern California in collaboration with colleagues based in Taiwan, China and Scotland. The study involved plucking hair from the backs of mice. This might have some similarity with people, but it's clearly not completely the same. Researchers tend to use mice as a first step in their research when they have a theory they want to investigate without subjecting humans to experiments. If the experiments in mice look helpful – say, in curing baldness – the researchers eventually try it in people. But the results in people aren't always the same as results in mice, so we shouldn't let our hopes climb too high!

The results showed hair regeneration depended on the density at which hairs were removed. Researchers describe how the hairs seemed to have a "sense and response" process that works around a threshold". If hair removal – specifically plucking – was below this threshold, there was no biological response to repair and regrow the hair, and the mice remained bald. However, once the plucking threshold was crossed, the plucked hair regrew – and often more hair regrew than was there originally.

This effect is known as quorum sensing. Quorum sensing is a biological phenomenon where, as the result of a range of different signalling devices, individual parts of a group are aware of the total population of that group. This means they can respond to changes in population values in different ways.

But we don't know whether the same thing would happen in people and it's certainly too early to claim that plucking hairs can cure baldness, as the Mail Online headline suggests: that may actually do more harm than good. For example, people with Trichotillomania, a condition where they impulsively pull out their hair, end up with patches of hair loss and balding that does not regrow. There may be specific stress-related reasons why this is the case, but it is a reminder not to take these mouse results at face value.

Philip Murray of Dundee University, one of the authors of the study, summed this up when he said: "It would be a bit of a leap of faith to expect this to work in bald men without doing more experiments."