Many cancer patients have an operation (surgery) to remove the cancer. In order to make sure all cancer cells have been removed or killed, the doctor may order chemotherapy. The chemotherapy will go throughout the body killing off any cancer cells it finds. These cancer cells could not be seen by the doctor doing the surgery.
The word chemotherapy means the use of any medicine to try to kill cancer cells. Chemotherapy, also called, chemo, can happen over a long period of time and may be done using pills, injections or intravenous (injecting liquid slowly into a vein).
Depending upon what type of cancer you have, there are different medicines that the doctor gives you. For me, I have two medicines that I take every week and one of them attacks and kills fast growing cells in my body. Hair cells are fast growing and are killed along with the bad cancer cells.
So a cancer patient like me can lose their hair not because we are sick with cancer, but because the medicine to make us better makes us lose our hair. This is not forever. Hair grows back after I stop the medicine, but it takes a long time. Sometimes it can take up to two years to grow enough hair to go to the hair dresser for a cut.