Hormones and genes are the main reasons people lose their hair, but a number of other factors can come into play, from illnesses to medication. Here are a few:
- Illnesses: Diabetes, lupus and thyroid gland disorders can all cause hair to fall out. Infections of the scalp can leave scarring that prevents hair from growing. Having a very high fever can slow new hair growth.
- Cancer treatment: Chemotherapy and radiation can lead to hair loss, but the hair will typically grow back after treatment is finished.
- Medications: Drugs to treat arthritis, depression, heart problems, high blood pressure and gout, as well as birth control pills, all can have hair loss as a side effect.
- Childbirth: Hormones rise during pregnancy that alter the hair cycle and prevent hair from falling out. After the baby is born, the normal cycle resumes and all the hair that would have been shed during pregnancy falls out.
- Hair treatments: Chemical bleaches, dyes, straighteners and perms all can damage hair and cause it to break if they're especially harsh or aren't used correctly. Also styling with tight rollers or cornrows can pull on the hair until it breaks and scars the follicle, preventing future hair growth.
- Smoking: It's unhealthy in so many ways, and researchers have now found that smoking also leads to an increased risk of baldness. A study in the 2007 Archives of Dermatology found that Asian men who smoked at least 20 cigarettes a day were more likely to be bald than those who didn't smoke. The authors say smoking might damage hair follicles.