In a study that may offer new hope for balding individuals and singles who dig a stylish coif on their partner, scientists have discovered that plucking 200 hairs in a certain pattern, within a small area, can stimulate 1,200 of them to grow back.
Waxing enthusiasts may wish to reexamine their technique.
As a dermatologist, study author Chih-Chiang Chen, a visiting scholar at the University of Southern California from National Yang-Ming University and Veterans General Hospital, Taiwan, knew that not only the follicle but also the area surrounding it is impacted by the injury caused by plucking.
It responds by provoking hair regeneration, says USC Stem Cell Principal Investigator Cheng-Ming Chuong of USC, and together the researchers reasoned it could be possible to activate more follicles based on this information.
They tested the hypothesis on mice, plucking 200 follicles -- one by one-in a variety of patterns.
The team found that establishing a circular plucking area of a diameter between three and five millimeters induced the thickening of hair, for plucking 450 of them in this way led to the regrowth of 1,300.
On the flipside, targeting an area that exceeded six millimeters in diameter and plucking hairs that were well spaced from each other resulted in no hairs regenerating -- but the researchers did not say whether this would be a good strategy for permanent hair removal.
The mechanism behind their pluck-to-thicken method is called "quorum sensing," or how a system responds to targeted stimuli that affects select members.
The team conducted a molecular analysis, concluding that the follicles signal distress to neighbors, releasing inflammatory proteins that call upon immune cells to conglomerate at the scene of the crime.
Here, the immune cells secrete molecules that, in large numbers signal both the plucked and un-plucked follicles to grow hair.
"The implication of the work is that parallel processes may also exist in the physiological or pathogenic processes of other organs, although they are not as easily observed as hair regeneration," says Chuong.
The study was published in the journal Cell, the same journal that in 2011 published a study in which researchers at Yale identified stem cells within the skin's fatty layer they say are signal hair growth.
One of the newest treatments for hair loss is the iGrow Hair Growth System, a machine that employs red light technology to promote hair growth.
The machine (priced at $695) is recommended for men whose balding patterns fall into categories IIa through V on the Hamilton-Norwood hair loss scale and for women whose hair loss patterns fall under Ludwig Baldness Scale Classifications of I to II.
It's recommended that potential users of iGrow have Fitzpatrick skin phototypes I to IV.