Everyone loses hair on a daily basis, usually an average of about 50 to 150 hairs per day. When the follicle is healthy, this hair is quickly replaced. When the follicle is no longer producing hair or when hair cannot be replaced as fast as it is falling out, baldness is the result.

The most common type of baldness is male pattern baldness. Its medical name is androgenetic alopecia. Why does male pattern baldness occur? In some men, the hair follicles on their head are sensitive to a chemical produced in the body called dihydrotestosterone, or DHT -- a hormone. As the sensitive hair is exposed to the chemical, it becomes dry, brittle and weak, eventually falling out. The follicle dies so no new hair grows in to take its place. Many of the men who experience this condition find that the hair on the sides of the head remains healthy, even though it is exposed to the same amount of DHT as the hair on top of the head.

Some women may experience baldness, for the same reason that men do. Around menopause, estrogen levels drop off. When this happens, the DHT their bodies is produce is no longer being counteracted and hair that is sensitive to DHT experiences the same effect as men's hair. Women do tend to lose hair in a different pattern, however. While men tend to lose hair in the temples and on the top of the head, women tend to develop thinner hair all over the scalp. Full bald patches are rare in women.

This type of hair loss is genetic, and the reason for about 95 percent of all hair loss, however, hair follicles can be weakened and destroyed through other means, as well, including:

• Some medications, especially the chemotherapy that is used to treat cancer patients, are notorious for causing hair loss.
• Illness, like diabetes and lupus and other autoimmune diseases can cause the loss of hair.
• Nutritional deficiencies, especially during crash dieting or eating disorders like anorexia, lead to hair loss. Getting enough protein and iron in your diet is essential for maintaining a healthy head of hair.
• Scarring caused by trauma to the head destroys hair follicles and leads to bald patches.
• Mistreatment of hair, including heavy bleaching or other chemicals, and blow-drying. Take good care of your hair if you want it to last a lifetime.
• Tight hairdos, like braids, pull on the follicle and eventually weaken and destroy them.