Possible side effects of radiotherapy

Radiotherapy can cause side effects. They usually begin after the first two weeks of treatment. After treatment ends, side effects may continue for several more days. But they gradually improve a few weeks after you finish treatment. Side effects are sometimes more severe if you have radiotherapy together with chemotherapy.

Your healthcare team will talk to you about what to expect before your treatment starts. It’s important to tell them about any side effects you have during or after your treatment. This is because they will often be able to help.

Side effects can include:

  • tiredness
  • changes to your skin
  • sore throat and difficulty swallowing
  • dry mouth or throat
  • thick, sticky saliva
  • voice changes
  • loss of appetite
  • loss of taste
  • hair loss
  • breathing problems.

Smoking may make side effects worse. It can be hard to give up but there is support available. Ask your doctor or nurse about help with giving up smoking.

About side effects of radiotherapy

Radiotherapy can cause some general side effects. These usually disappear gradually over a few weeks or months after treatment finishes.

How you are affected will depend on the dose of radiotherapy, the length of your treatment and the size of the area being treated. Side effects can be more severe if you have radiotherapy combined with chemotherapy.

Side effects usually begin to develop after two weeks of radiotherapy. They may continue to get worse for 7 to 10 days after treatment ends before starting to gradually improve. Most people find that their side effects improve about 4 to 8 weeks after radiotherapy finishes, or when combined treatments end.

Before you start your treatment, your doctor, nurse, speech and language therapist, dietitian or radiographer will discuss your treatment with you so you know what to expect. Let them know about any side effects you have during or after treatment, as there are often things that can be done to help.

Tiredness (fatigue)

Radiotherapy often makes you feel tired, especially towards the end of treatment and if you’re travelling a long way each day. Try to rest regularly. It can help to balance this with some gentle physical activity, such as short walks. This will help you feel more energetic.

Skin changes

The skin at the front of your neck will gradually become red or darker. If you’re dark skinned, your skin may get darker or develop a blue or black tinge. Your skin may also feel sore and itchy, like sunburn. Skin changes can vary depending on the amount of radiotherapy you have. Changes usually start about two weeks after radiotherapy begins and last until about four weeks after it finishes.

Your radiographer or specialist nurse will tell you how to look after the skin in the treated area. During your treatment, you will usually be advised to do the following:

  • Wear loose cotton or natural fibre clothing next to your skin with no tight collars. When you’re outside, use a scarf to protect your skin from the sun or cold winds.
  • Wash your skin gently with soap or aqueous cream and lukewarm water and gently pat it dry.
  • Use a moisturiser that is sodium lauryl sulphate (SLS) free. Your radiographer can give you more information about this.
  • Avoid using scented products on the treated area, as these can irritate the skin. Check with your radiographer or nurse before you put anything on your skin in the treated area.
  • Avoid rubbing the skin.
  • Avoid wet shaving until a few weeks after your radiotherapy treatment. You can use an electric razor instead.
  • Avoid the sun and use a high-SPF sunscreen. Your radiographer can give you more information about this.

If you develop a skin reaction, such as soreness or a change in skin colour, let the radiotherapy staff know as soon as possible. They will advise you on the best way to manage it.

After your treatment has finished, you’ll need to protect the skin in the treated area from strong sunshine for at least a year and cover the area with a light scarf. Once any skin reaction has settled down, you should use a suncream with a sun protection factor (SPF) of at least 30.

The radiotherapy staff will advise you on how to look after your skin. They can prescribe creams for you to use if your skin becomes very sore. If your skin peels or cracks, you may need a dressing on the area. A district nurse or practice nurse from your GP surgery can do this for you or teach you or a friend or relative how to do it.

Sore throat and difficulty swallowing

The lining of your throat may become sore and inflamed, making it difficult to swallow. Your doctor can prescribe liquid painkillers to help with this. Try to take these before meal times to help make eating easier.

Your speech and language therapist will talk to you about any swallowing or eating difficulties that you may have. It’s important to try to continue to eat and drink for as long as possible during your treatment.

You may cough when you eat and drink. Sometimes this can be a sign that food and drink is going down the wrong way (into the airway). This can cause a chest infection. Your speech and language therapist can teach you exercises to help with swallowing and prevent food and drink going down the wrong way.

Your specialist nurse, radiographer, dietitian or speech and language therapist will give you advice on foods that are easy to swallow. They may also give you nutritious or high-calorie drinks. Most people manage to eat soft, moist foods while their throat is sore. Some people can only manage a liquid diet. The soreness usually lasts for a few weeks after the radiotherapy has finished, but may continue for longer, depending on the area treated.

Some people find the soreness stops them eating or drinking enough. This is more common if you have radiotherapy and chemotherapy at the same time (chemoradiation). If this happens, your doctor might suggest you have nutritional support so that you don’t lose too much weight. This means giving you liquid food that contains all the nutrients you need, through a feeding tube that goes into your stomach. You can also have liquids and medicines through the tube. If your doctors think you might have problems with eating, they may suggest you have a feeding tube put in before starting your treatment.

Nutritional support can:

  • prevent weight loss
  • make sure you’re getting enough fluids and nutrients
  • help you feel less weak or tired
  • ease the pressure of having to eat
  • allow the sore area to heal
  • allow you to eat smaller amounts when eating is uncomfortable.

The liquid feeds can be given through one of the following:

  • A thin tube that’s passed up your nose and down into your stomach (called a nasogastric or NG tube). This type of tube is usually only used if you are an inpatient.
  • A tube that’s put through the skin and into the stomach (called a percutaneous endoscopic gastrostomy or PEG tube).

Your doctor and dietitian will talk to you about this and explain which tube is likely to be best for you. You may need help with nutrition before radiotherapy if you have lost a lot of weight or have swallowing problems. Having liquid feeds through a tube will give you enough calories to help prevent any unplanned breaks in your treatment. Your nurse or dietitian will help you look after your feeding tube and show you or a relative or friend how to care for it when you are at home.

Your speech therapist will assess whether you can still swallow food and fluids safely while you have a tube in. You will still be encouraged to eat and drink with a tube in place, even if you can only manage small amounts at a time.

Once your treatment has finished, you are usually encouraged to try to stop using the tube as soon as possible. It’s important to follow the advice of your hospital team when you have a feeding tube in.

Dry mouth or throat

Radiotherapy to the larynx may affect the salivary glands, making you produce less saliva. The lining of your mouth and throat can become dry. This can make eating and speaking difficult.

Saliva helps keep your mouth clean. So it’s important to brush your teeth with a soft toothbrush twice a day and to use mouthwashes as explained to you by your doctor or nurse. Try drinking sips of water regularly throughout the day to keep your mouth moist. Your doctor can prescribe artificial saliva sprays and gels to help. You are less likely to get an infection if your mouth is moist.

Some people may have a dry mouth for several months after treatment has finished. For some people, it may be permanent. It depends on the size of the area being treated. Your doctor will be able to tell you how likely this is.

We have more information about coping with a dry mouth.

Thick, sticky saliva (mucus)

You may have a build-up of sticky mucus in your throat. It’s a good idea to always have tissues handy, as you might need to spit often to get rid of this. Rinsing your mouth and drinking water regularly can help with the mucus. Your doctor or specialist nurse may suggest that you use a nebuliser. This is a machine that produces a fine mist of fluid, which you inhale.

Voice changes

Your voice may already be hoarse and it may get worse during radiotherapy. Your doctor will tell you about the risk of permanent voice changes. Try to rest your voice by not straining it and avoid smoky places. Your voice should gradually improve and get stronger after your radiotherapy is over. This may take several weeks. A speech and language therapist can advise you on how to look after your voice during treatment and suggest voice exercises to speed up your recovery.

Loss of appetite

You may not feel like eating if your mouth is sore. This can be at its worst towards the end of radiotherapy and in the first couple of weeks after it’s finished. It’s important to try to eat, even if you don’t feel like it. Sometimes it can help to have painkillers before you eat if your mouth is feeling very sore. You can also see a dietitian, who may ask you to have some high-calorie or nutritious drinks until your appetite returns.

Loss of taste

Your sense of taste may change or you may find everything tastes the same. This should get better, but it may take a few months and sometimes up to a year after radiotherapy has finished. Occasionally, taste can be affected permanently.

Hair loss

Radiotherapy may cause some temporary hair loss over the back of your head. If you have any facial hair, it may fall out and this can be permanent.

Breathing problems

Radiotherapy may cause swelling in your throat. Very rarely, this can lead to breathing problems, which need to be treated straight away.

If you develop any difficulties with your breathing or if your breathing sounds different, tell a doctor or contact the hospital as soon as possible. Very rarely, people need an operation to help them breathe. This is called a temporary tracheostomy, and it should be short term.


If you are a smoker and continue to smoke during a course of radiotherapy treatment, it can make the radiotherapy less effective and increase the risk of side effects. Giving up smoking can be difficult, but there’s lots of support available. Speak to your doctor or call a stop-smoking helpline for further advice and to find out where your local stop-smoking service is.

Back to Radiotherapy explained

Planning your treatment

Your specialist will plan your radiotherapy carefully to make sure it’s as effective as possible.

Before your radiotherapy

Before you start radiotherapy, your team will explain what your treatment involves and how it may affect you.

Making a radiotherapy mask

During radiotherapy to the head and neck a mask is used to help you keep still so that exactly the right area is treated.

Your radiotherapy team

You will meet many different specialists from your radiotherapy team. You may see them before, during and after radiotherapy treatment.

After treatment

It can take time to recover from radiotherapy. Support is there if you have any problems.