Telogen effluvium, a type of hair loss, occurs when large numbers of follicles on the scalp enter the resting phase of the hair growth cycle, called telogen, but the next growth phase doesn’t begin. This causes hair to fall out all over the scalp without new hair growth.Telogen effluvium does not generally lead to complete baldness, although you may lose 300 to 500 hairs per day, and hair may appear thin, especially at the crown and temples.
A medical event or condition, such as a thyroid imbalance, childbirth, surgery, or a fever, typically triggers this type of hair loss. Telogen effluvium may also occur as a result of a vitamin or mineral deficiency—iron deficiency is a common cause of hair loss in women—or the use of certain medications, such as isotretinoin, prescribed for acne, or warfarin, a blood thinner. Starting or stopping oral contraceptives (birth control pills) may also cause this type of hair loss.
Telogen effluvium usually begins three months after a medical event. If the triggering event is temporary—for example, if you recover from an illness or stop taking the medication causing the hair loss—your hair may grow back after six months. Telogen effluvium is considered chronic if hair loss lasts longer than six months.