Gray hair is caused by a reduction of melanin in which layer of the hair?

• A. Medulla
• B. Cortex
• C. Cuticle
• D. Cortex and cuticle

Answer: (B)

Gray hair results from a reduction of melanin in the cortex, the middle layer of the hair shaft that carries most of the pigment. The cortex contains pigment granules that give hair its color, so when melanin production or retention in this layer decreases, the hair looks gray or white. The cuticle is the outer protective layer and doesn’t carry pigment, while the medulla is the inner core and not the primary site of color. Therefore, the cortex is where melanin reduction most directly causes gray hair.