Hair growth relies on genes that promote the development of new hair cells. This takes place within the hair follicles, the small openings that cover the scalp as well as the rest of the body. A number of chemicals are needed to trigger the production of hair cells, and one of the most important of these is the human growth factor.
Scientists suggest that the derma roller works by triggering the production of human growth factor. When the needles are rolled along the skin, they cause minor surface wounds to the tissue. The body then must work to produce new skin in the area of the wound and releases the human growth hormone and other chemicals to assist with this process. Supporters of the derma roller believe that when these chemicals are released they also stimulate the growth of hair in the affected area, which can help begin regrowth in areas of thinning.