Nioxin System 4 Scalp Treatment with an SPF of 15 (formerly Cytonutrient Protectives Treatment) is an intense leave-in scalp treatment especially formulated for noticeably thin-looking, chemically enhanced hair (see more scalp than hair). It provides scalp and hair protection from damaging chemical residue, environmental toxins and DHT buildup. This unique foam nourishes scalp and hair with powerful chaperone molecules ensuring scalp assimilation of essential vitamin nutrients.