A certain amount of hair loss about 50 - 200 per day is normal as hair goes through cycles of growth and rest. About 10% of hair is in the rest phase at any one time and will eventually fall out and new hair will grow in its place. Excessive hair loss or alopecia may occur as a diffuse thinning or in a patchy distribution. The reasons for alopecia are many according to our guest blogger consultant, Dr. Patricia Wong. These include the following:
- Genetic predisposition called androgenetic alopecia is the most common cause for thinning. This can be inherited from the maternal or the paternal side of the family. It can start as early as in the teenage years.
- Thyroid abnormalities which may be in the form of an over active or under active thyroid function. This can be reversed with proper treatment.
- Anemia or iron deficiency.
- Alopecia Areata in which hair completely falls out in round patches usually the size of a coin leaving a smooth skin. The cause is unknown.
- Severe infection, high fever, chronic illness or major surgery may cause a temporary hair loss which usually corrects after several months.
- Medications such as those used for high blood pressure, depression or for cancer treatment.
- Excess intake of vitamin A.
- Hormonal changes such as in taking birth control pills, post pregnancy or menopause.
- Excessive or rapid weight loss.
- Protein deficiencies such as in crash dieting or in malnutrition.
- Skin infections of the scalp such as ringworm infection.
- Chemical treatments to the hair such as coloring or perms especially when done improperly or too often.
- Stress or Depression.
The hair loss may occur several months after the onset of any of these events. The "pull test" is one method which may be used to assess if the hair loss is normal. Hold 60 hairs between the thumb and the index and middle fingers then pull gently but firmly. If six or fewer hairs are pulled out then the shedding may be normal, but if more than six hairs are pulled out then active hair shedding may be occurring. Patients should not shampoo their hair 24 hours before the test is performed.
To determine the cause, it is recommended to see your health care provider and a dermatologist who specializes in hair disorders. An examination of the hair and scalp, blood tests and some times a biopsy may be required to fully assess the cause of the hair loss.
There is no scientific evidence showing efficacy of over the counter shampoos and treatments to stimulate hair growth. It is best to be evaluated by a specialist so that an effective treatment can be prescribed when possible.
References: American Academy of Dermatology. Dr Patricia Wong, board certified dermatologist specializing in diseases of skin, hair, and nails, practicing in Palo Alto. Shapiro J, Wiseman M, Liu H. Practical management of hair loss. Can Fam Physician 2000;46: 1469-77.