This week a study was published by the University of Southern California that prompted the tabloids to claim that plucking hair from sparse, balding heads could promote regrowth from dormant follicles. "At last, a cure for baldness!" the Daily Mail cried, amidst a myriad of other sources. But these claims in the headlines are unsubstantiated, says the NHS. Here's how it all breaks down...

The study was carried out on mice, not humans. Scientists carried out a 'plucking' procedure on various sized areas of skin and in varying densities. So, for example, they plucked 200 hairs equally spaced over an area 3mm in diameter and the same amount over a 5mm diameter. They found that over a larger area a lot more new hairs regrew, but that it had to be in a concentration of at least roughly 20% to see any new growth at all.

However, mice have a much higher follicle density than that of the human head, with human hair being less than 10 times the density of mouse hair. Furthermore, the study made absolutely no implications for human use whatsoever.

In simple terms, this study never said that it was a cure for human baldness. And it couldn't, since there is no one type of baldness. In a study last year, a successful treatment for alopecia areata was discovered that was unlikely to have implications for androgenetic alopecia.

There may be, however, implications based on the reason for this phenomenon, namely quorum sensing. Quorum sensing is a communication method used by bacteria to enable them to determine how many of said bacteria are present in a local population, and is particularly used in the coordination of gene expression. In this study, it would have been utilised to determine the activity of hair stem cells. The above image shows that the plucking of hairs induces death of the hair-building cells, or keratinocytes, which in turn triggers an immune response that provokes all the follicles in the region to enter the anagen (growing) stage. In the 5mm diameter area this forced hair growth even further away from the plucked area.

See the highly misleading Daily Mail article here, and the much more informative NHS write-up here.