As you know, laser hair removal works only on pigmented hair. It will not work on white hair or hair that has lost the capacity to create pigment. Hairs produce pigment only in the anagen phase or the active growing phase. On a beard, most of the hair is always in the anagen phase. On the legs, the percentage will range between 40% and 60% in the anagen phase, but it can be even less in the anagen phase. This means you have to wait until the hair cycles into the anagen phase before laser hair removal will work on body hair. This can take months to happen. You probably need to separate laser hair removal visits into longer intervals. The first thing that happens when hairs move into the resting phase, or telogen, is the lost of pigment production. Without pigment, the laser will not be affective. We also find that laser hair removal does not work on transplanted hair from the back of the scalp to the top of the scalp even though there is pigment in the hair follicles of transplanted hairs. It may be that the scar tissue formed around the graft limits the affects of the laser in transplanted hair. I have never seen a good reason why lasers don't work in transplanted hair, but it shows that there are reasons why lasers do not work in all instances. I do know that lasers will cause hair to fall out from grafted hair, but the hair invariably grows back. One other theory might be that a low energy caused a temporary shedding of hair but did not kill the hair. Rather, the tissue surrounding the outer root sheath was produced a protective scar that might limit the benefit of laser hair removal in the future.
