Hair loss caused by the radiation and
chemotherapies used to treat cancer. Radiation and chemicals used in cancer treatments work to kill the cancer and often cause hair to stop growing as well: They are designed to kill cells that reproduce very rapidly like those produced in the hair papilla.
Hair cells, like cancer cells, are readily affected by the toxic effects of select chemotherapy and radiation. Hair usually starts to fall out in clumps at a rapid rate within 3 weeks of the first treatment. Hair can literally fall out overnight. Hair growth generally becomes normal shortly after treatments are stopped.
About Hair Loss 