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What are the side effects of radiation therapy?

Medically reviewed by Last updated on Nov 8, 2023.

Official answer


Common side effects of radiation, depending on the body area being irradiated, include; hair loss, nausea and vomiting, dry mouth, difficulty swallowing, shortness of breath, diarrhea, erectile dysfunction, sunburn like rash, tiredness, and menstrual changes.

Radiation therapy is a common treatment for certain types of cancer. It uses high-energy x-rays, gamma rays, electron beams or protons to shrink solid tumors or damage cancer cells and stop them from growing and multiplying.

Like other cancer treatments, radiation can cause side effects, because it can damage healthy cells and tissues near the radiation area, although advances in technology mean radiation therapy is much more precise than it used to be. Actual side effects vary from person to person depending on the location and type of cancer, the dose of radiation therapy, and a person’s general health.

Common side effects according to body area being irradiated include:

  • Head and neck: Dry mouth, mouth and gum sores, difficulty swallowing, jaw stiffness, nausea, lymphedema (swelling of the lymph nodes), or tooth decay
  • Chest: Difficulty swallowing, shortness of breath, breast or nipple soreness, and shoulder stiffness. The combination of a cough, fever and a feeling of fullness in the chest may signal radiation pneumonitis which typically happens between two and six weeks after radiation therapy. Untreated radiation pneumonitis may lead to radiation fibrosis which involves permanent scarring of the lungs
  • Stomach and abdomen: Nausea and vomiting or diarrhea
  • Pelvis: Bladder irritation, diarrhea, incontinence, or rectal bleeding
  • Genital area (men): erectile dysfunction, lowered sperm counts or reduced sperm activity leading to lowered fertility
  • Genital area (women): Menstrual changes, symptoms of menopause, or infertility.

Other side effects include:

  • Hair loss if radiation is aimed at a part of the body that grows hair
  • A rash that looks like a severe sunburn (known as radiation recall) that appears on the irradiated part of the body. Rare, but more common if certain types of chemotherapy are given after external beam radiation therapy
  • Skin dryness, itching, blistering, or peeling
  • Tiredness and fatigue.

Side effects usually start during the second or third week of treatment and may last for several weeks after the final treatment. Some side effects can be prevented, and most can be treated.

With radiation therapy, there is always a risk of developing a second cancer; however, the benefits of treatment are considered to far outweigh the risks in most patients.

For more information about radiation therapy see here.

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