Is there a limit to how often you can get PRP injections, and is there evidence that results will plateau at any point?

Thank you for your interesting question.  I suspect that the reason you do not have any doctor answers yet is that we really don't know the answer and there are likely variables that impact this differently in each different individual.  Theoretically, there should not be a limit regarding how many PRP treatments one can have - from a safety perspective, that is.  Regarding whether one can expect the same results every time or if there might be a plateauing effect - again, I cannot give you a straight answer, because, as far as I am aware, no one has performed a scientific study that might answer this question.  We know that the platelets will produce many different growth factors in the region into which they are injected and that those growth factors are what we believe cause the beneficial effects observed. Your reasoning is sensible though, in that I would expect that no matter how many growth factors you expose your tissues to, there may be an upper limit with respect to the observed response.  That response, however, is not permanent and whatever symptoms we were attempting to treat with the PRP injections, after a time, the PRP effects will wane as the regenerated tissue ages.  That may be anywhere from weeks to months to years, depending upon the area treated, the age of the individual, and many other factors.  At that point, re-treatment should result in a positive response. You will have to observe for yourself if you feel that repeated treatments are not giving you the same results as the earlier ones.  If that were to happen, then I would consider getting the treatments less often and pay close attention to  your results.

PRP for cosmetic use is a fairly new technique. There are not many studies looking at the benefits for facial rejuvenation, hair restoration, or even in pain management. This includes osteoarthritis, ligament and tendon injuries, and various musculoskeletal problems etc.
The simple answer is we don't know. Some studies have used 2-6 treatments spaced 10-14 days apart.
Dr. Anna Sylwestrowicz MD, FRCP(C)
Victoria, BC