Hair we can see is a dead protein called keratin. Keratin is colorless and arranged in overlapping scales which makes hair flexible. The hair cortex contains pigment that gives hair its color. Hair with abundant pigment is black; less is brown or red, and no pigment white. Hair grows about 6 inches a year from the living root. Balding results from reduced hormone levels in both men and women. Each follicle has a small muscle that raises and lowers the hair, trapping warm air in winter and blocking out the sun in summer. Hair glands produce an oily lubricant called sebum that keeps hair from drying out. A yeast eats sebum, irritating the scalp causing cells to die. Dead cells appear white and are called dandruff.