System 4 is specially designed for noticeably thinning, fine, chemically-treated hair. It delivers denser-looking hair while protecting the scalp and providing moisture balance to coloured hair. Helps to remove follicle-clogging sebum» SEBUM The sebaceous glands are microscopic glands in the skin that secrete an oily/waxy matter, called sebum, to lubricate and waterproof the skin and hair of mammals. In humans, they are found in greatest abundance on the face and scalp, though they are distributed throughout all skin sites except the palms and soles. In the eyelids, meibomian sebaceous glands secrete a special type of sebum into tears. There are several related medical conditions, including acne, sebaceous cysts, hyperplasia, sebaceous adenoma and sebaceous gland carcinoma , fatty acids and environmental residues from the scalp skin and hair. Cleanses to provide thicker-looking hair. Gently massage into scalp and hair, Rinse well. then follow with Nioxin scalp Revitaliser.