system 1 duoSYSTEM 1 SHAMPOO: Nioxin's Cleanser System 1 Cleansing Shampoo for naturally thinning hair is the first step in a three part dioxin regimen, specially formulated to strengthen hair to prevent breakage and enhance hair texture. It prepares the hair and scalp for a complete hair thickening treatment with Nioxin's three part System 1. This professional, skin purifying cleansing shampoo removes dirt, excess oil, and other environmental residues from the