Side effects of radiotherapy

Radiotherapy to the head can cause side effects. Most of these disappear gradually after treatment finishes. Your doctor, nurse or radiographer will explain likely side effects and tell you how they can be managed.

Common side effects include tiredness, itchy sore skin on your scalp, hair loss and headaches.

You’ll need plenty of rest. Some weeks after treatment, you may have an extreme tiredness called somnolence. This improves over the weeks. You’ll be given advice on looking after your skin and your hair will usually grow back after treatment. Tell your doctor if you have headaches. They can prescribe painkillers or steroids to help.

Sometimes side effects get worse after treatment but this is temporary. Let your doctor know if this happens.

Radiotherapy to the head may cause side effects months or years after treatment. Newer ways of giving radiotherapy help protect healthy tissue and reduce the risk of late effects. Some possible late side effects include changes in your memory or developing a cataract. Talk to your doctor if you are concerned about late side effects.

Side effects during or after treatment

You may develop side effects over the course of your treatment. These usually disappear gradually over a few weeks or months after treatment finishes. Your doctor, nurse or radiographer will discuss this with you so you know what to expect. Let them know about any side effects you have during or after treatment. They can give you advice on how to manage them. Stereotactic radiotherapy may cause fewer side effects.

Tiredness (fatigue)

Radiotherapy can make you tired so try to get as much rest as you can, especially if you have to travel a long way for treatment each day. Tiredness can continue for several months after treatment has finished. Balancing rest and activity throughout the day is important as your body needs rest to recover from the treatment.

Somnolence is an extreme tiredness some people may get after radiotherapy to the brain. It happens about 4–8 weeks after treatment. You may have very little energy, feel drowsy and spend a lot of time sleeping. This gradually gets better over a few weeks.


Some people have headaches during radiotherapy. Let your doctor know if this happens. They can prescribe painkillers to control these. Radiotherapy can cause swelling and increased pressure. If your headache is caused by this, your doctor will prescribe steroids to treat it.

Hair loss

You will lose the hair in the area being treated and there may be some hair loss on the opposite side of your head where the rays exit. Your hair will usually grow back within 2–3 months of finishing treatment. Sometimes it grows back a slightly different colour and may be thinner than before. Some people’s hair may not grow back. This depends on how much radiotherapy you had.

Skin irritation

Your skin in the treated area may get red, dry, itchy and feel sensitive or sore. Dark skin may get darker. Your nurse or radiographer will give you advice on looking after your skin. If it becomes sore and flaky, let them know. Your doctor can prescribe creams to help this.

Skin reactions usually settle down 2–4 weeks after radiotherapy.

Your radiographers will check your skin but you should let them know if it feels sore.

Here are some tips to help with skin irritation:

  • Don’t put anything on the treated area of your skin before checking with your nurse or radiographer.
  • Wash your hair or scalp gently with lukewarm or cool water. Use non-perfumed shampoo or soap.
  • Pat your hair or scalp dry gently with a soft towel. Don’t rub it and avoid using a hair dryer.
  • Wear a scarf or hat to protect your head from the sun or cold until any reaction settles down.
  • If you shave your head, use an electric razor instead of wet shaving.
  • Avoid exposing your head to the sun during treatment and for at least a year afterwards. Cover up or use suncream with a sun protection factor (SPF) of at least 30.

Feeling sick

You may feel sick. This can be treated effectively with anti-sickness drugs (anti-emetics). Your doctor can prescribe these. If you don’t feel like eating, you can try replacing meals with nutritious, high-calorie drinks. You can get these from most chemists and some can be prescribed by your doctor.

We have more information about these side effects, visit be.macmillan or call us on 0808 808 00 00 and we can send you the information you need.

Some people find the side effects temporarily get worse after their treatment has finished. You may feel low or worry your treatment isn’t working. But it’s usually a reaction to the radiotherapy or because your steroids may have been reduced or stopped. It’s important to let your doctor or nurse know straight away if your side effects get worse.

Late effects

Radiotherapy may cause side effects that develop months or years after treatment. These are called late effects. Newer ways of giving radiotherapy are designed to limit the amount of healthy tissue affected and reduce the risk of late effects.

Your specialist will talk to you about the risk of late effects before your treatment starts. Let them know if you’re worried about particular side effects. The benefits of having radiotherapy treatment will far outweigh the risk of developing late effects.

Possible late effects include:

  • Changes to your memory, thinking and reasoning. This is called intellectual impairment.
  • Developing a cataract if you have radiotherapy close to your eye. The clear lens of the eye becomes cloudy and blurred and you can’t see as well. Cataracts can usually be easily treated with a small operation.
  • Changes in your hormone levels if your treatment involves the pituitary gland. This could lead to problems with your periods, sex drive or your thyroid gland.
  • Developing a second cancer in the treated area years later. This is a rare possible late effect.

At your clinic visits, your doctor and nurse will talk to you and check for any late effects of treatment.

Back to Radiotherapy explained

Who might I meet?

You will meet many different specialists before, during and after radiotherapy treatment.