Nioxin System 4 Scalp & Hair Treatment for colored, dry and damaged hair with progressed thinning is the final step of the three-part system, which amplifies hair texture while protecting against breakage. This volumizing leave-in helps to provide thicker looking hair by refreshing the scalp and increasing the fullness of each hair strand. Nioxin Scalp Treatment stimulates growth through increased blood circulation, which can give a temporary reddening effect and a warming sensation when applied. Use with Nioxin System 4 Cleanser Shampoo and Conditioner for best results.