Why do chemotherapy drugs designed to fight cancer also commonly cause a person's hair to fall out?

Chemo hair loss: Chemo affects the anagen phase (growing phase of hair follicle). This type of hair loss is associated with chemotherapy because the toxic effect of the chemotherapy that is designed to stop the cancer cells from growing and dividing. Chemotherapy is not selective and it negatively impacts all cells-healthy and cancerous- including hair follicles.