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Health Encyclopedia - Diseases and Conditions

Hair Loss

Definition of Hair Loss
Description of Hair Loss
Causes and Risk Factors of Hair Loss
Treatment of Hair Loss
What Questions To Ask Your Doctor About Hair Loss

Definition of Hair Loss

Article updated and reviewed by Michael S. Lehrer, MD, Clinical Assistant Professor, Department of Dermatology, University of Pennsylvania on April 18, 2005.

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Description of Hair Loss

Each hair grows in cycles—it grows, rests, and then falls out. Usually, this cycle repeats approximately yearly. At any time, about ninety percent of a person's scalp hair is 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 of 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.

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Causes and Risk Factors of Hair Loss

A number of causes might be identified. These include:

Childbirth. When a woman is pregnant, her hair continues to grow. The usual 50 to 100 hairs per day are not shed. However, after she delivers her baby, many hairs enter the resting stage of the hair cycle at once. Within two to three months after delivery, these hairs may all fall out together and be seen as large amounts of hair coming out in their brushes and combs.
High fever, severe infection, major surgery, significant life stressor. From four weeks to three months after a person has a high fever, severe infection, major surgery, or significant life stressor such as death in the family, 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, acne, or psoriasis, and some medications for heart problems.
Cancer treatment drugs. Most 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 beginning chemotherapy. The patient may lose all of his hair, but this will usually 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.
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. This type of hair loss also runs in families.
Infections. Ringworm, or tinea capitus, is a common fungal infection in children. Patches of hair may be lost and replaced with pink scaly skin.

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.

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Treatment of Hair Loss

If hair loss is caused by a temporary situation such as medication, stress or insufficient iron, however, however, the hair loss will stop when its cause ends. Hair loss due to infection may require oral antibiotics or antifungals. Alopecia areata can be treated with injections of steroids such as triamcinolone into the area. For all of the causes, early treatment works the best.

For hair loss caused by androgenic alopecia, there is no cure, although many treatments are available. Finasteride (Propecia) is a prescription hair loss treatment that is prescribed for men only. Minoxidil (Rogaine) is rubbed directly onto the scalp and works for both men and women. It usually works best for hair loss at top and back of the scalp, where there is still some remaining hair. This is available over the counter at most pharmacies.

Well chosen hairstyles can often hide hair loss effectively. Partial hairpieces or wigs are recommended if hair loss is severe.

Finally, hair transplantation has improved dramatically over the last several years. During a hair transplant, healthy hairs are harvested from an area of the scalp with normal hair growth. Individual hairs are then placed into areas of hair loss. When done well, the result is extremely natural appearing.

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