Nioxin System 4 Scalp & Hair Treatment for colored hair with advanced thinning is the final step in a three-part Nioxin routine, which strengthens the hair's structure and prevents breakage. This volumizing leave-in helps to give hair a thicker appearance by refreshing the scalp and increasing the fullness of each strand. Nioxin Scalp Treatment stimulates growth through increased blood circulation, which can cause temporary redness and a warming sensation upon application. Use together with Nioxin System 4 Cleanser Shampoo and Nioxin System 4 Conditioner for best results.