Nioxin cleansing shampoo removes dirt and debris that normally block hair follicles. It also actively removes follicle-clogging sebum, which often contains a hormone called DHT (seen as a major factor in alopecia). Acting as a DHT blocker, therefore, means that Nioxin cleanser can promote hair growth. The active ingredient in the Nioxin hair regrowth treatment is 2% or 5% minoxidil.