Nioxin System 1 Scalp & Hair Treatment for natural hair with slight thinning is the final step in a three-part Nioxin routine, which strengthens the hair 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 1 Cleanser Shampoo and Nioxin System 1 Conditioner for best results.