There are two categories of side effects for radiotherapy: the short term and the long term.
The short term begin almost immediately after treatment, and they will depend on where on the body the treatment is taking place. Treatment over the abdomen will cause nausea. Your skin may get red and itchy, almost like a sunburn. Infertility could result if the reproductive areas are treated. There will be general irritation in any spot. Hair loss will occur a couple weeks after treatment begins.
Long-term effects can develop months after treatment, or sometimes years after. These effects will again be different depending on the area treated, but they include: thickening of the skin, nerve damage, or damage to organs, specifically the heart and lungs.
