Radiation therapy is a common part of the treatment plan for many types of cancers. It uses targeted doses of radiation to kill cancer cells or slow their growth.

Sometimes, radiation is the only treatment you need. But in most cases, doctors combine it with other treatments like chemotherapy or surgery. Doctors use it:

  • before other treatments to shrink a tumor
  • after other treatments to destroy any remaining cancer cells
  • to reduce symptoms if the cancer is not curable

Along with killing cancer cells, radiation therapy can also damage healthy cells. This can cause many side effects. Side effects will depend on the type and amount of radiation, as well as the organ systems affected.

Here’s more information on what kinds of side effects to expect and some advice on how to manage them.

Early vs. late side effects

Early side effects typically happen within weeks of starting radiation treatment. Many of these side effects improve once radiation treatment finishes. Early side effects may include fatigue, nausea, skin changes, and hair loss.

Late side effects may not appear until after your radiation treatment ends. For example, if you have radiation to your chest area, it’s possible to develop lung or heart disease months or years later. It’s important to continue to follow up with your cancer care team to monitor for long-term effects.

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Everyone will respond differently to radiation therapy. Side effects will depend on the location of the radiation treatment. Still, some side effects are common, regardless of where you received treatment.

Radiation affects your cells’ ability to divide. Cells that grow and divide the fastest are the most affected. This includes cancer cells but can also include:

  • skin cells
  • hair cells
  • blood cells
  • cells in the digestive tract

Here are some of the most common side effects of radiation.


Fatigue is a very common effect of radiation. Your body needs a lot of extra energy to heal and recover from treatment.

This is not typical fatigue that extra sleep will fix. This kind of fatigue can make it very hard to get through the day.

Fatigue will be worse if radiation has also resulted in anemia. Anemia can develop if radiation kills too many red blood cells. These cells carry oxygen around the body. Low levels of red blood cells are a major cause of fatigue in people with cancer.

Here are some tips to help you manage:

  • Rest when you can.
  • Ask for help with household tasks.
  • Prioritize your energy.
  • Take any iron supplements for anemia as directed by your doctor.
  • Consider gentle movement as a way to boost your energy levels.
  • Practice relaxation strategies, such as meditation, yoga, or massage.

Skin problems

Skin cells are prone to damage from radiation because they divide so quickly. Radiation can affect your skin at the site where you’re getting treatment.

Your skin may get red and itchy or appear darker. These changes often happen within a few weeks of starting radiation. Some people may get permanent scarring.

Here are some tips to help:

  • Use gentle soaps and skin care products to prevent further irritation.
  • Avoid further damage from the sun by wearing long sleeves and pants, and using sunscreen and SPF lip balm.
  • Use caution with things that may cause more damage, such as heating pads or shaving.
  • Keep nails trimmed to avoid accidental damage from scratching your skin.

It’s important to talk with your radiation care team before starting to use any specific lotions or soaps. Some types can worsen skin damage if you apply them before your daily treatment.

Hair loss

Hair thinning or loss can happen in the area doctors treat with radiation. Greater amounts of radiation will usually cause greater amounts of hair loss.

Hair often starts to grow back within 3 to 6 months after radiation finishes. There may be changes in the texture or thickness when it grows back.

If you have lost hair on your head, your scalp may be sensitive. Consider wearing a hat or head covering to protect it. If you decide to wear a wig, make sure it fits well and does not cause further irritation.

Appetite changes

Many people who have radiation therapy will notice changes in their appetite. There are many reasons for this. Fatigue, changes in taste and smell, dry mouth, or nausea can all make it hard to eat.

This side effect can start early in treatment. For many people, it gets better once treatment finishes.

Here are some things you can try:

  • Keep simple, ready-to-eat snacks around.
  • Set a timer to remind you to eat every few hours.
  • Sip on nutritional supplement drinks or smoothies.
  • If you have a metallic taste in your mouth, use bamboo or plastic utensils to eat instead of metal utensils.
  • Rinse your mouth several times a day to help with a dry mouth or an unpleasant taste. Avoid alcohol-based mouthwashes like Listerine. These can be irritating and make your dry mouth worse.
  • Explore whether moving around helps improve your appetite.
  • Try bland, soft foods if your mouth is sore.
  • Choose cold foods without a smell if you’re nauseated.

Does radiation therapy make me radioactive?

There are different methods of radiation therapy. The two main types are external beam and brachytherapy:

External beam radiation targets a dose of radiation directly at a tumor. The radiation damages and kills cancer cells. There’s no radiation left in your body from this treatment.

Brachytherapy places a source of radiation inside your body near the tumor. Radiation from the implant targets the cancer cells. You may give off some radiation while the implant works inside your body. Once a doctor removes the implant, you can no longer give off radiation.

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You may have other side effects depending on the site of radiation therapy. Radiation techniques have improved to reduce damage to other cells. But areas around the tumor are often still affected by radiation.

Your doctor and cancer care team can help you find ways to manage side effects.

Below are some specific side effects of different radiation sites.

Treatment for brain cancer may involve a few targeted sites of higher dose radiation. It could also be a lower dose of radiation used on a larger area of the brain. Your doctor will discuss the best plan for you.

Some side effects are delayed and can start 1 or 2 years after treatment. Short-term side effects are related to brain swelling from the effects of radiation.

Side effects of radiation to the brain can include:

  • changes to the skin or hair on your head
  • headaches
  • trouble with speech
  • memory challenges
  • nausea and vomiting

Medications may help reduce swelling in the brain to prevent or manage side effects.

Radiation to the head and neck can damage the cells in the lining of your throat and mouth. Many side effects happen because of that cell damage. There may also be changes in skin, nerve, and bone function.

Other possible side effects include:

  • dry mouth
  • mouth sores
  • jaw stiffness
  • changes in sense of smell or taste
  • swallowing difficulties
  • tooth decay
  • swelling in the gums

Many of these side effects can make it hard to eat enough. The cancer itself may also make eating difficult.

Some people find they can better tolerate soft, bland foods. Getting more nutrients from smoothies or nutritional supplement drinks may help. If you’re struggling to eat enough, talk with a doctor or a registered dietitian for support.

Treatment for lung, breast, or esophageal cancer often involves radiation to your chest. Side effects can vary depending on the part of the chest undergoing treatment.

Side effects may include:

  • heartburn
  • difficulty swallowing
  • breast soreness or swelling
  • cough

Radiation to the chest area can potentially damage the heart and lungs. Heart disease may be a long-term effect of radiation. It may include:

  • an irregular heartbeat
  • hardening of the arteries
  • heart failure

Another possible effect of radiation in the chest area is inflammation in the lungs. This is called radiation pneumonitis. People with other lung conditions are more likely to develop it.

Symptoms of radiation pneumonitis may start 3 to 6 months after radiation. They include shortness of breath, cough, and chest pain.

Radiation for breast cancer may also increase the risk of long-term lung and heart damage. With more targeted treatments, this is happening less often.

Typical side effects of radiation to the breast include:

  • swelling or fluid buildup in the breast (lymphedema)
  • breast soreness
  • redness or other changes in skin color

Some of these changes won’t go away even after treatment ends. There should be no new changes in your breast if it’s been over 1 year since your last radiation treatment. If you notice anything new, talk with your healthcare team.

Radiation to your abdominal area can cause digestive changes. These side effects are usually short term. They often get better within 2 to 3 weeks of finishing treatment.

Side effects may include:

  • diarrhea
  • stomach cramps
  • nausea
  • vomiting
  • bloating
  • gas

Sometimes, dietary changes can help. You can try some of the following:

  • Eat small, frequent meals.
  • Eat cooked vegetables instead of raw vegetables.
  • Try bland foods without a strong flavor or smell.
  • Try foods with softer textures that may be easier to digest.

Some medications may help you manage side effects. Talk with a healthcare professional about your options.

Radiation to your pelvis can be a treatment for cancers such as bladder or ovarian cancer. Side effects may include digestive changes, just like radiation to your abdomen.

In addition, you may also have the following side effects:

  • bladder infections
  • pain when having a bowel movement
  • changes to fertility
  • changes in sexual function
  • changes in bowel and bladder control

Radiation is known to affect fertility. If you have concerns about future fertility, discuss them with your healthcare team.

You may have radiation therapy to treat rectal cancer. If you have colon cancer, you may have radiation with chemotherapy. Radiation is not usually the only treatment for colon cancer.

Side effects of radiation to the rectum include:

  • diarrhea or painful bowel movements
  • bowel incontinence
  • nausea
  • irritation to the bladder
  • changes in sexual function

These side effects typically get better after treatment ends.

Many short-term side effects of radiation therapy will resolve within weeks or months of finishing therapy. But some effects can be long term.

Everyone experiences the side effects of radiation therapy a bit differently. It will depend on the:

  • type of radiation
  • amount of radiation
  • type of cells affected

Skin cells, hair cells, and many cells in your digestive system are sensitive to radiation. They damage easily. They also grow quickly, and side effects improve as new cells grow back.

Sometimes, cells are not able to repair themselves, resulting in long-term side effects.

Heart damage from radiation to the chest area may show up 10 to 30 years after radiation treatment ends.

Can radiation therapy increase your risk of other cancers?

According to a 2018 research article, people who have had radiation therapy have a slightly higher risk of developing another cancer. But the benefit of using radiation to treat cancer usually outweighs the future risk.

Long-term follow-up is important for anyone who has had cancer. This provides a chance to catch any changes in your health early. If a second cancer does develop, there are more treatment options in the early stages.

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There’s ongoing research to see whether medications can reduce damage to the salivary glands. This is a common issue for people getting radiation for head and neck cancers. The dry mouth and swallowing challenges from radiation damage are often long lasting.

A doctor may recommend amifostine. But research is split on whether it’s helpful. There are also several side effects from its use.

Other medications used to manage radiation side effects may include:

  • antiemetics for nausea and vomiting
  • medications to manage diarrhea
  • steroid medications to reduce inflammation
  • topical agents, including for the treatment of mouth sores
  • medications to manage pain

There’s a lot to learn about cancer and the use of radiation as a treatment. Your doctor and cancer care team are great resources.

Here are several common questions you may have about radiation therapy.

How soon after radiation therapy do side effects start?

The timing of side effects can vary a lot. Some will start within days or weeks of starting therapy. Others don’t happen until months or years after treatment ends.

Does radiation have more or fewer side effects than chemotherapy?

Many of the side effects of chemotherapy and radiation are similar. Both treatments work to kill cancer cells. Both also damage healthy cells in the process.

Radiation can be a more targeted therapy. In some cases, there are fewer side effects than chemotherapy.

The type and severity of side effects from either treatment will also depend on the:

  • type of cancer
  • type and doses of chemotherapy or radiation used
  • duration of treatment
  • area of the body undergoing treatment

For many people, both radiation and chemotherapy may be part of the treatment plan.

Should I limit contact with people during radiation?

External beam radiotherapy targets the radiation at the tumor to kill cancer cells. There’s no lingering radioactivity. You don’t need to worry about being radioactive at any time during or after treatment.

If you have internal radiation therapy (brachytherapy), you may need to be cautious. Brachytherapy involves placing a contained dose of radiation near the tumor. While it’s active in your body, you may give off a bit of radiation.

While it’s active, you may need to limit contact with all people. You may just need to avoid pregnant people and young children. This will depend on the radiation dose.

Is radiation therapy safe for older adults?

Yes. Both external beam radiotherapy and brachytherapy are safe for older adults. Radiation can be an important part of improving the quality of life for older adults with cancer.

Sometimes the cancer is not curable, or surgery is not an option. Radiation can help shrink the tumor to reduce symptoms.

Radiation therapy is a common treatment for many types of cancer. It targets cancer cells to damage and kill them. Doctors may use radiation to eliminate cancer or shrink a tumor to reduce its effects.

Side effects from radiation happen when radiation damages otherwise healthy cells. Common side effects of any type of radiation include fatigue, appetite changes, hair loss, and skin changes. Some side effects are more specific to the site undergoing treatment.

Side effects may be short term and improve once treatment ends. Other side effects are more permanent. There is also the potential for effects to occur months or years after treatment ends.