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Hair Loss
Carol Stark, M.D.
Hair can define how we see ourselves, as far as personality and attractiveness. While hair loss can be frustrating and embarrassing, it is much more common than you may think. We each have about 100,000 hairs on our scalp and you need to lose about 50% of your hair before the loss becomes noticeable.
A hair follicle is a part of the skin that creates hair by packing cells together. The activity of a hair follicle has three phases, a growth phase (anagen), a transitional phase (telogen) and a resting phase (catagen). For scalp hair the growth phase typically lasts two to three years, although it can be longer. The transitional phase lasts two to three weeks and the resting phase lasts three to four months. At the end of the resting phase the hair falls from its shaft and the next cycle is begun. Normally 80 to 90 percent of scalp follicles are in the growth phase at one time. Typical hair shedding is 75 to 100 hairs a day.
The most common cause of hair loss is androgenic alopecia, which in men is commonly called male pattern baldness. However, it affects both men and women, but is easier to camouflage in women who experience a more diffuse hair loss. For women the incidence increases at menopause.
A common cause of diffuse hair loss is telogen effluvium, a reversible loss of mature cells. It is associated with a stressful event, including medical illness, surgery, weight loss or psychological stress. The stressful event will cause more hair follicles to enter the resting phase (telogen). Then three to four months later the hair loss is noted.
Anagen effluvium is the term for hair loss that occurs in the growth phase of the hair cycle. Since 80 to 90 percent of the hair is in the growth cycle at one time, this can be a significant hair loss. A common cause of anagen effluvium is chemotherapy.
There are many other causes of hair loss including medication and medical diseases such as thyroid disease. Trauma to the hair can also cause hair loss. Examples of hair trauma include some styling techniques or chemicals. Hair loss can also be caused by scarring and infection, including fungal infections of the scalp.
If you are concerned about your hair loss, see your family health provider who will ask you questions, examine you, possibly order some tests and suggest treatment.
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