SYSTEM 6 - CHEMICALLY TREATED HAIR - FOR PROGRESSIVE THINNING HAIR. Strengthen and moisturize your hair with Nioxin’s 3-part System 6 Scalp Therapy Conditioner for Chemically Treated Hair with Progressed Thinning. With its Smooth Plex technology, this professional hair care product helps retain moisture balance and smoothing control. Lightweight, Nioxin’s density-protecting conditioner is specially designed for chemically treated hair with progressed thinning and leaves it thicker, fuller-looking. Nioxin’s Scalp Therapy Conditioner is the second step of a 3-part Nioxin regimen, designed to strengthen the hair and amplify hair structure.