It is normal to lose between 50 and 100 hairs a day. With about 100,000 hairs on the scalp, that small loss isn’t noticeable. New hair normally replaces the lost hair, but this doesn’t always happen. Hair loss can develop gradually over years or happen abruptly. Hair loss can be permanent or temporary.
In some cases, hair loss may occur with a simple halt in the cycle of hair growth. Major illnesses, surgeries, or traumatic events can trigger hair loss. However, your hair will usually start growing back without treatment.
Hormonal changes associated with pregnancy, childbirth, discontinuing the use of birth control pills, and menopause can cause temporary hair loss.
Medical conditions that can cause hair loss include thyroid disease, alopecia areata (an autoimmune disease that attacks hair follicles), and scalp infections like ringworm. Diseases that cause scarring, such as lichen planus and some types of lupus, can result in permanent hair loss because of the scarring.
Hair loss can also be due to medications used to treat cancer, high blood pressure, arthritis, depression, and heart problems.