Why hair loss happens

Hair loss occurs because chemotherapy targets all rapidly dividing cells—healthy cells as well as cancer cells. Hair follicles, the structures in the skin filled with tiny blood vessels that make hair, are some of the fastest-growing cells in the body. If you're not in cancer treatment, your hair follicles divide every 23 to 72 hours. But as the chemo does its work against cancer cells, it also destroys hair cells. Within a few weeks of starting chemo, you may lose some or all of your hair.

Some chemotherapy drugs affect only the hair on your head. Others cause the loss of eyebrows and eyelashes, pubic hair, and hair on your legs, arms, or underarms.

The extent of hair loss depends on which drugs or other treatments are used, and for how long. The various classes of chemotherapy drugs all produce different reactions.

The timing of your treatments will also affect hair loss. Some types of chemotherapy are given weekly and in small doses, and this minimizes hair loss. Other treatments are scheduled every three to four weeks in higher doses, and may be more likely to cause more hair loss.