Normal Hair Loss:
We all lose about 100 hairs per day, out of the 100,000 contained by the average scalp. This is due to a few factors:
- Lifespan: The average lifespan of a single hair is 4.5 years; the hair then falls out and is replaced within 6 months by a new hair.
- Styling: Shampooing, blow drying, and brushing hair can all cause a few hairs to fall out; most of us do this regularly.
- Aging: After the age of 30 (and often before), men and women both start losing hair, though men tend to do so at a faster rate.
Genetic hair loss isn’t due to excessive amounts of hair falling out, as many believe, but to an insufficient amount of hairs growing back to replace the hairs that have been shed. Hereditary baldness is associated with a few factors:
- Gender: Hereditary, or “pattern” baldness, is much more common in men than in women.
- Age: By age 30, 1 in 4 men is balding; by age 60, 2 in 3 men are balding or bald.
- Hormones: Pattern baldness is associated with testosterone; women who have more of it in their system as they age tend to lose (or, technically, fail to re-grow) more hair. This is also why more men experience pattern baldness.
You may have heard that stress can cause hair loss, and it’s true. Excessive physical or emotional stress, like that associated with injury, illness or surgery, can cause one of two types of hair loss:
- The more common type is called telogen effluvium. With this less severe type of hair loss, the hair stops growing and lies dormant, only to fall out 2 or 3 months later. Then it grows back within 6 to 9 months.
- The other type of stress-induced hair loss is known as alopecia areata, and involves a white blood cell attack on the hair follicles. With this type of hair loss, the hair also falls out within weeks (usually in patches), but can involve the entire scalp and even body hair. Hair may grow back on its own, but treatment may also be required.
There are other factors that can also cause hair loss, including but not limited to:
- Hormonal changes
- Pregnancy, childbirth, and birth control pill usage
- Nervous habits
Medline Plus and MayoClinic.com