A blue brush with hair in it against a white background.
Some common side effects of radiation therapy are hair loss and skin irritation.

Radiation Therapy Side Effects

Radiation therapy involves using high doses of radiation to kill cancerous cells and slow their growth. It is an effective treatment, but it can also cause a variety of radiation therapy side effects.

This article explains the most common radiation therapy side effects and how to manage them.

What is Radiation Therapy?

During radiation therapy, doctors use high doses of radiation therapy to destroy cancer cells, slow their growth, and shrink tumors. It can also help to relieve some cancer symptoms, such as pain.

Radiation damages cancer cells’ DNA, stops them from dividing, and causes them to die. The body can then break down and remove the damaged cells. Radiation therapy can be external or internal.

External Radiation Therapy

External radiation therapy involves using a machine to fire a powerful beam at the affected area. It can move around the body to aim its beam at the cancer from different angles. It is a local treatment that is suitable for cancer in one area of the body.

Internal Radiation Therapy

Internal radiation therapy involves placing a source of radiation inside the body. There are two types: brachytherapy and systemic therapy.


Brachytherapy involves using solid radiation sources, including ribbons, capsules, or seeds. Doctors place these items in or close to the cancerous area.

Systemic Therapy

Systemic therapy uses liquid radiation sources, such as oral medicine, intravenous infusions, or injections. This liquid travels around the body, seeking out and destroying cancer cells.

What Cancers Does Radiation Therapy Treat?

Different types of radiation therapy can treat different types of cancer. External beam radiation therapy and brachytherapy are local treatments. They are useful for treating cancer that is in one area of the body.

External radiation therapy is one of the most common treatments and can be used for many different types of cancer. However, brachytherapy is most often used for cancers of the:

  • Head
  • Neck
  • Eyes
  • Breast
  • Cervix
  • Prostate

Systemic therapy is used to treat cancers that have spread throughout the body. There are different types of systemic therapy that are effective for different cancers. For example, a treatment called radioactive iodine (I-131) is used for certain thyroid cancers. Another example is radionuclide therapy, also known as molecular radiotherapy. It is sometimes used to treat advanced prostate cancer.

What is the Radiation Therapy Treatment Process Like?

Before beginning radiation therapy, patients will have a consultation with an oncologist (a cancer doctor). They will decide upon the most appropriate type of treatment and oversee the process. They may also order scans and other tests to determine the exact location and size of the cancer.

The patient must then give their permission to begin treatment. Before starting external radiation, it is common practice to carry out a simulation. This will give the patient an idea of what to expect during the sessions.

It is important to be comfortable during the treatment as it is necessary to stay very still. This might involve using aids like tape, foam supports, headrests, or plaster casts. If you feel uncomfortable during the simulation, discuss this with your oncology team.

After the simulation, the treatment plan will be reviewed and any changes made if necessary. Before beginning treatment, tiny but permanent marks are made on the skin. These show the radiation technician where to aim their beam.

The machine used for external radiation therapy can be quite noisy and may produce a strange smell. This is normal and not a cause for concern.

Treatment is usually given five days a week (Monday to Friday) and each session lasts approximately 15 minutes. The total duration of treatment varies, but it often lasts three to nine weeks.

The process for internal radiation therapy is a little different. Patients may require anesthesia and to stay in the hospital during treatment. Internal radiation therapy can cause the patient’s body to give off radiation for a while after treatment. Therefore, they might be advised to stay in hospital and avoid contact with others for a few days as a precaution.

Side Effects of Radiation Therapy

Like any treatment, radiation therapy can cause side effects. They will vary from patient to patient depending on the type of treatment, dosage, treatment area, and general health. Some of the most common radiation therapy side effects include:

You May Also Like


It is common to feel physically, mentally, and emotionally tired during radiation treatment. These side effects often get progressively worse as treatment goes on. They can also last for weeks or months after treatment ends as it takes time for the body to recover.

Patients should speak to their oncologist if they experience:

  • Fatigue that does not improve, keeps coming back, or becomes worse
  • Feeling more tired than usual after activity
  • Confusion or difficulty concentrating
  • Inability to get out of bed for more than 24 hours
  • Disruptions to their daily routine or social life

Skin Changes

External radiation can damage the skin, including:

  • Redness
  • Irritation
  • Blistering
  • Swelling
  • A sunburned or tanned appearance

After a few weeks, the skin may become itchy, flaky, and dry. This condition is called radiation dermatitis.

Hair Loss

Radiation can cause hair thinning and loss in the treatment area. The hair usually grows back but it may be thinner or have a different texture than before.

Local Side Effects

Additional side effects may also occur depending on the area being treated. For example:


  • Nausea and vomiting
  • Headache
  • Blurred vision

Head and Neck:

  • Mouth changes, such as dry mouth, soreness
  • Dental problems
  • Taste changes
  • Throat changes, including difficulty swallowing
  • Reduced thyroid gland activity


  • Swelling
  • Tenderness


  • Throat changes, including difficulty swallowing
  • Cough
  • Shortness of breath

Stomach and Abdomen:

  • Diarrhea
  • Nausea and vomiting
  • Urinary and bladder changes


  • Diarrhea
  • Nausea and vomiting
  • Sexual and fertility problems
  • Urinary and bladder changes


  • Diarrhea
  • Sexual and fertility problems
  • Urinary and bladder changes

Long-Term Side Effects

In some cases, radiation therapy side effects can occur months or years after treatment ends. For example, there is a low risk of developing another cancer in a different area.

How to Manage Radiation Therapy Side Effects

Some oncologists prescribe medicine called radioprotective drugs for certain types of treatment. They reduce the risk of some radiotherapy side effects. For example, a drug called amifostine can offer protection against mouth changes during head and neck radiation therapy.

However, not all doctors agree on how these medications should be used. Therefore, it is often a case of managing side effects as well as possible. Some helpful tips include:

Managing Fatigue

  • Rest as much as possible
  • Ask friends and family for assistance in day-to-day activities
  • Ask employers for time off if necessary
  • Engage in regular light exercise if possible
  • Try to eat a balanced diet with enough calories and protein

Skin Changes

  • Wear loose fitting clothing made from smooth, soft, and natural fabrics
  • Wash with lukewarm water and a mild soap
  • Pat yourself dry rather than rubbing with a towel
  • Do not rub, scrub, or scratch the affected area
  • Do not apply adhesive tape to the affected area
  • Do not use hot or cold packs and avoid washing in hot water
  • Avoid shaving if possible, or use an electric razor if necessary
  • Reduce sun exposure by wearing protective clothing and SPF 30 sunscreen
  • Check with your oncology team before applying any products to the skin

Hair Loss

  • Protect the skin with a hat or scarf
  • If wearing a wig, ensure it does not irritate the skin

The National Cancer Institute offers a selection of helpful guides with more information on managing radiation therapy side effects, including Support for People With Cancer and Eating Hints Before, During and After Treatment.