The sebaceous gland a hair follicle secretes sebum, a type of oil that in healthier hair gives hair that lustrous look and feel. But what occur is one does sweat often but don't cleanse the hair and scalp, then the oil becomes waxy and dries swiftly. Over time you get a save of layers of dried sebum that slowly chokes the hair follicle until new hair cannot make its way through the follicle allow it to...