The follicles in the human scalp are active for two to six years, and then they rest for about three months. Shorter hairs, such as those in the eyebrows and eyelashes, grow for about 10 weeks and then rest for 9 months. The human scalp contains an average of about 100,000 hairs. From 5 to 15 per cent of the hairs in the scalp are in the resting stage at any time. A person sheds from 70 to 100 hairs a day from follicles that are in the resting stage.
Many factors affect the growth of hair.
They include age, diet, general health, and changes in the seasons. For example, hair grows faster in children than in adults, and it grows faster in summer than during any other season. Cutting or shaving hair on any part of the body does not have any effect on the future growth or texture of the hair. Disorders of the hair and scalp Baldness occurs if the follicles on the scalp die and no longer produce new hair. Heredity is the most common cause of baldness.