Cancer is a disease in which certain cells in the body mutate and begin to grow uncontrollably. Most normal cells have a 'trigger' or 'off switch' to tell them to stop growing at a certain point . . cancer cells lose that ability. Some types of chemotherapy were created to target a cancer cells uncontrolled 'growth' . . the idea is to kill the cancer cells by using a medication that will stop it from 'growing'. The medication will kill all cells in the human body that 'grow' . . and hair cells grow . . the medication cannot tell the difference between a cancer cell and a hair cell . . so it kills them both. Thus a cancer patient will lose their hair. Once the chemotherapy is stopped or treatment is done than the hair will grow back
