According to the American Board of Dermatology, hereditary hair loss affects an estimated 50 million men and 30 million women in the United States. It can occur in women as early as their 20s, and in men as early as their teens.
By age forty, 40 percent of women and nearly 40 percent of men have visible signs of hereditary hair loss. By age fifty, 50 percent of both genders show signs of the condition.
About 90 percent of a person's scalp hair is continually growing, a phase that lasts between two and six years. Ten percent of the scalp hair is in a resting phase that lasts between two and three months. At the end of its resting stage, the hair goes through a shedding phase. Shedding 50 to 100 hairs a day is considered normal. When a hair is shed, it is replaced by a new hair from the same follicle located just beneath the skin surface. Scalp hair grows about one-half inch a month. Hair is made up a form of protein, the same material that is found in fingernails and toenails. Everyone, regardless of age, should eat an adequate amount of protein to maintain normal hair production. Protein is found in meat, chicken, fish, eggs, some cheese, dried beans, tofu, grains and nuts. Abnormal hair loss can be due to many different causes, but about 50 percent of the population experience normal hair loss by the time they reach 50. People who notice their hair shedding in large amounts after combing or brushing, or whose hair becomes thinner or falls out, should consult a dermatologist.
Hair loss is caused by a number of factors, including aging, heredity, and an over-sensitivity of affected hairs to male hormones. Hair loss begins in some people as early as their teens.
Genetic predisposition to hereditary hair loss can be inherited from either side of a person's family tree or from both parents. It is found in men and women of most ethnicities and nationalities.
The many number of causes of hair loss include:
- Childbirth. When a woman is pregnant, she does not lose as much hair as usual. However, after she delivers her baby, many hairs enter the resting stage of the hair cycle. Within two to three months after delivery, some women may see large amounts of hair coming out in their brushes and combs.
- High fever, severe infection, flu. From four weeks to three months after a person has a high fever or a severe infection or flu, he or she may be shocked to see a lot of hair falling out. This condition usually corrects itself but may require treatment.
- Thyroid disease. Both an overactive and underactive thyroid can cause hair loss. The hair loss associated with thyroid disease can be reversed with proper treatment.
- Inadequate protein in diet. Some vegetarians, people who go on crash diets that exclude protein, and those with severely abnormal eating habits, may develop protein malnutrition. When this happens, a person's body will help to save protein by shifting growing hairs into the resting phase. Massive hair shedding can occur two to three months later. Hair can then be pulled out by the roots. This condition can be reversed by eating the proper amount of protein.
- Medications. Prescription drugs can cause temporary hair shedding in a small percentage of people. Examples of such drugs are blood thinners, some drugs used to treat gout and arthritis, and some medications for heart problems.
- Cancer treatment drugs. Certain types of drugs used in chemotherapy will cause hair cells to stop dividing. Hair shafts become thin and break off as they exit the scalp. This can occur one to three weeks after chemotherapy. The patient may lose up to 90 percent of the natural scalp hair. The hair will re-grow after treatment ends.
- Birth control pills. Women who lose their hair when taking birth control pills usually have an inherited tendency towards hair thinning.
- Low serum iron. Iron deficiency sometimes produces hair loss. Low iron can be detected by laboratory tests and corrected with iron pills.
- Major surgery or chronic illness. Anyone who has a major operation - a tremendous shock to the system - may notice increased hair shedding within one to three months afterwards. This condition reverses itself within a few months. People who have a chronic illness may shed hair indefinitely.
- Alopecia areata. In this type of hair loss, hair usually falls out, resulting in totally smooth, round patches about the size of a coin or larger. This disease may affect children, women or men of any age.
- Androgenic alopecia. This is the most common type of hair loss and is often called "male- or female-pattern baldness". The hair usually thins out first in the front of the scalp and moves progressively to the back and top of the head. It tends to be progressive.
See a doctor if you experience hair loss at the same time as you experience the following symptoms: skin problems, breathing problems, poor appetite or unexplained weight loss, vomiting, fever, pain, constipation or diarrhea.