Hair goes through 3 phases in its life cycle: growth (anagen), rest (catagen) and loss (telogen). At any given time, 90% of your living hair is in a growth phase. If your existing hair continues to grow in length (requiring cutting) then at least some of your hair is still in growth phase, and Procerin can help you regrow your hair. If none of your hair ever lengthens or requires cutting, Procerin's effectiveness is limited to retaining your existing hair.