Not only are the defenses down, but you have no way to battle it either. Nausea - This will likely come as well. They do have medicines that help eliminate it, but not always. Nicole ended up getting sick to her stomach and having heartburn further along in the treatments. In the beginning she was able to eat anything she wanted including pepperoni, pizza, candy, soda, sausage, etc.
Radiation is simply a concentrated x-ray aimed at a tumor site.
It basically burns the tumors cells. It doesn't hurt when they do it unless you are having difficulty getting into position for treatment, but afterwards it can create a very bad sunburn. One thing about the burn though is that you really can't put anything on it. Any greasy substance can deflect the beam or reduce it's effectiveness. Not just any doc, the radiation oncologist.