Facts about Hair

1. 07

   Keratin, the primary protein in hair, comprises approximately 95 percent of each strand's dry weight and also forms the outer layer of human skin and fingernails.

   HairMay 14sharechemistrybiologystructure
2. 06

   Androgenetic alopecia affects approximately 50 million men and 30 million women in the United States, with male pattern baldness linked to sensitivity to the hormone DHT and typically beginning between ages 20 and 40.

   HairMay 14sharebiologymedicinegenetics
3. 05

   Blonde hair contains approximately 150,000 strands while black hair averages around 100,000, making lighter hair appear thicker due to increased follicle density.

   HairMay 14sharebiologymeasurementgenetics
4. 04

   Gray hair results from the depletion of melanin-producing stem cells in follicles, with most people experiencing their first gray hairs between ages 30 and 35.

   HairMay 14sharebiologyagingchemistry
5. 03

   Each human hair strand contains three distinct layers: the outer cuticle, the middle cortex, and the inner medulla, with the cortex comprising roughly 80 percent of the hair's total mass.

   HairMay 14sharebiologyanatomystructure
6. 02

   Approximately 100 strands of human hair fall out daily as part of the normal growth cycle, with each follicle producing hair for 2 to 6 years before entering a resting phase.

   HairMay 14sharebiologymeasurementphysiology
7. 01

   The average human scalp contains approximately 100,000 hair follicles, with each strand growing about 6 inches per year.

   HairMay 13sharebiologymeasurement