Side Effects of Radiation Therapy

Author: Courtney Misher, MPH, BS R.T.(T)
Last Reviewed: January 08, 2024

Each person can have different side effects from radiation therapy. Some side effects depend on the type of cancer and area being treated. It is important to talk to your radiation team about possible side effects and how to manage them.

Short-Term Side Effects

There are two main types of side effects: acute and chronic. Acute (short-term) side effects occur during the treatment and often go away a few weeks after treatment is done. They may include fatigue, skin reactions, and side effects specific to the area being treated.


  • Is a feeling of exhaustion, feeling completely worn out, feeling that the body is "heavy" and hard to move, or an inability to concentrate. Fatigue can cause physical, emotional, and mental exhaustion.
  • This fatigue is not caused by too much activity. It is not usually relieved by rest, yet many people say rest can lessen fatigue.
  • Fatigue is the most common acute side effect of radiation therapy. It is believed to be caused by the large amount of energy that is used by the body to heal itself in response to radiation therapy.
  • Most people begin to feel fatigued about 2 weeks after radiation treatments begin. The tired feeling goes away gradually after the treatment is finished. Normal levels of energy generally return a few weeks after treatment is done. If you have received other treatment this can take up to a year. For more information on fatigue, go to our article about fatigue.

Skin Reactions:

  • Many patients that receive radiation therapy develop a skin reaction. Small amounts of radiation are absorbed by the skin where the beam enters the body each time radiation is delivered. Over time, this can lead to a skin reaction.
  • About 2 to 3 weeks after your first radiation treatment, you may notice redness and irritation like a sunburn. The skin may be itchy, dry, red, or sore.
  • These changes are a normal part of your therapy and are temporary. In some cases, you may need to stop radiation treatments for a short period of time to allow the skin to heal. For more information on skin reactions, go to Side Effect: Skin reactions.

The other acute side effects of radiation therapy are typically specific to the area being treated. For example, patients receiving radiation therapy to the stomach or abdomen may have diarrhea and nausea and vomiting. Whereas patients receiving treatment to the head and neck area may develop mouth sores or esophagitis. Only patients receiving radiation therapy to the head have hair loss on the head, called alopecia. Your providers will tell you how to manage these side effects. For additional information see the Radiation Side Effects Menu.

Long-Term Side Effects

Chronic side effects can occur during treatment and last for many months or years after treatment, or they can develop months to years after radiation therapy. They differ according to the area treated and the total dose of radiation therapy received. Some possible long-term side effects include:

  • Changes to the heart and lungs.
  • Joint problems.
  • Changes in brain function.
  • Hearing loss.
  • Dental issues.

During your initial consultation, your radiation oncologist will talk to you about any side effects that you may have. You should consider this information when making decisions about your treatment.

After treatment, talk with your oncology team about receiving a survivorship care plan, which can help you manage the transition to survivorship and learn about life after cancer. A survivorship care plan can help you better understand the health risks you may face as a result of your cancer treatment and what you can do to reduce and monitor for those risks. You can develop your own plan using the OncoLife Survivorship Care Plan tool.


Coping – late effects. National Cancer Institute. (2021, August 6). Retrieved from

Radiation therapy side effects. American Cancer Society. (2020, December 10). Retrieved from


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