Most people routinely lose between 70 and 150 hairs from their scalp each day, mainly through washing, brushing, and combing. But there is tremendous variation in the number of hairs that people shed each day, depending on the number of scalp hairs and the length of the growth cycle. As people age, their rate of new hair growth slows down, resulting in a gradual thinning.
Scalp hair starts to thin when more hairs are lost through normal shedding than the scalp is able to renew. About 40% of the density of scalp hair has to be lost before thinning of the hair becomes noticeable.
Hair loss can be caused by:
o Heredity issues. Most balding is caused by a genetic predisposition - in other words, it's part of a person's genetic makeup. This is called male pattern baldness, or hereditary balding or thinning. It is the most common cause of thinning hair.
o Illness, certain physical conditions, or their treatments. This can include high fever, thyroid disease, childbirth, inadequate protein in the diet, iron deficiency, cancer treatments, the use of certain medications, and other causes.
Hair may be lost in two ways:
o In patchy hair loss, well-defined areas of hair are lost while the remaining scalp retains a good covering of hair.
o In generalized hair loss, there is a uniform thinning over the entire scalp with no areas of normal hair growth.
The medical term for hair loss is alopecia. There are different classifications of alopecia:
o Alopecia areata is a disease in which well-defined bald patches occur. It usually clears completely within 6 to 12 months without treatment.
o Alopecia totalis is an uncommon condition in which all hair on the scalp is lost. The cause is unknown, and the baldness is usually permanent.
o Alopecia universalis is a total loss of hair on all parts of the body.
o Androgenetic alopecia is balding caused by heredity. It can affect both men and women, although women with this inherited tendency do not become totally bald. The condition can start in a person's teens, twenties, or thirties.
If you notice you are shedding hair excessively after combing or brushing, or if your hair is becoming thinner, you should consult with your primary care provider or a dermatologist (a physician who specializes in treating skin and hair problems). A doctor can determine if disease is present and whether or not the hair loss will respond to medical treatment.