Possible side effects of radiotherapy

Your specialist will explain the most common side effects you might get and how they can be reduced or managed. If you have chemotherapy at the same time as radiotherapy (chemoradiation), the side effects are likely to be more severe.

You will usually find side effects improve within 6 to 8 weeks of radiotherapy finishing.

Some of the side effects you may have are:

  • sore and sensitive skin in the treated area
  • a sore mouth and throat
  • loss of taste
  • a hoarse voice
  • dry mouth
  • thick saliva
  • bad breath
  • tiredness.

Your specialist doctor, nurse or speech and language therapist and dietician can to help reduce any side effects. If your mouth and throat are sore, your specialist can prescribe painkillers to control this. There are ways to help a dry mouth and loss of taste, but it can sometimes take months to recover.

Radiotherapy reduces the amount of saliva you produce. Because saliva protects your teeth from decay, you will need regular dental and hygienist appointments after your treatment.

Side effects of radiotherapy

Radiotherapy to the head and neck can cause temporary side effects, such as a sore mouth or throat and difficulty swallowing. Side effects can be mild or more severe, depending on the size of the area being treated and the length of your treatment. They are usually more severe if you have radiotherapy combined with chemotherapy.

Side effects usually begin to develop after about 2 weeks of radiotherapy. They may continue for 7 to 10 days after treatment ends, before slowly improving. Most people notice an improvement in their side effects 6 to 8 weeks after radiotherapy has ended.

Sometimes radiotherapy can cause long-lasting side effects, or new side effects that develop months or even years later. These are called long-term effects and late effects. Two of the most common late effects are a dry mouth and an increased risk of tooth decay. It is very important to follow a regular mouthcare routine during and after radiotherapy.

Your specialist can tell you whether your treatment may cause any late effects. They will also tell you about things you can do to help reduce the risk of having problems.


What you can do to help reduce side effects

Look after your mouth

It is very important to look after your mouth during and after radiotherapy. Keeping your mouth as clean as possible can help protect your teeth, encourage tissue to heal and reduce the risk of problems in the future.

Stop smoking

Smoking during radiotherapy is likely to make your side effects worse. It also reduces the effect of radiotherapy on the cancer. If you smoke, stopping smoking will help your recovery. You can get information and support to help you stop.

Limit how much alcohol you drink

Alcohol, especially spirits, will irritate the areas affected by your treatment. So it is best not to drink alcohol or use mouthwashes containing alcohol during radiotherapy.

Eat a healthy diet

Eating can be hard during treatment, but it is important to get the nutrition you need. This helps your tissues heal, increases your strength and may also reduce your risk of having some long-term effects of radiotherapy.

If you are finding it difficult to eat, tell your specialist nurse, doctor or radiographer. They can refer you to see a dietitian, if you do not already have one. There are lots of things that can help make sure you get the food and nutrition you need.

Your doctor may recommend you have a feeding tube inserted if you are not able to eat enough and you are losing weight. The tube is usually in place for a few weeks while you finish your treatment, and can normally be removed when you start to eat and drink again.

If swallowing is a problem, a speech and language therapist (SLT) can give you advice and support.

We have more information about feeding tubes and how to cope with eating problems.


Sore and sensitive skin

Sore and sensitive skin

The skin on your face and neck will slowly redden or darken and may feel sore and itchy (a bit like sunburn). This usually starts after about 2 weeks of treatment and lasts for up to 4 weeks after radiotherapy has finished.

The radiotherapy team will advise you on how to look after your skin. They can give you painkillers and advice about caring for your skin until it heals.

Wash your skin gently with soap or aqueous cream and lukewarm water and gently pat it dry. It is very important to only use the soaps, creams and lotions that the radiotherapy team recommend, as chemicals in some products can make the skin more sensitive to radiation. Moisturisers need to be sodium lauryl sulphate (SLS)-free. Your radiographer can give you more information about this. They can prescribe creams for you to use if your skin becomes very sore. It is also best to avoid wet-shaving for a time, as your skin will be very delicate.

Loose, cotton clothing is less likely to irritate sore skin. It is also best to avoid clothes with stiff or tight collars.

The skin in the area being treated will be more sensitive to the sun during and after radiotherapy, especially in the first year. Covering up with a sun hat and a soft, cotton or silk scarf around your neck will help protect your skin from the sun. Once any skin reaction has disappeared, use a sun-protection cream with a high SPF of at least 30.

The radiotherapy team can talk to you about when and how to use sun-protection cream after your treatment.


Sore mouth and throat

Your mouth and throat are likely to become sore after a couple of weeks of treatment. You may also develop mouth ulcers. You will be prescribed painkillers to take regularly. Tell your cancer specialist if your mouth is still sore. You may need stronger painkillers, or you may have an infection in your mouth that needs treatment.

Towards the end of radiotherapy, your mouth is likely to be extremely sore and it can be painful to eat. You may need strong painkillers, such as morphine. Your doctor or specialist nurse can discuss this with you.

Your dietitian will see you regularly during treatment, as it can be difficult to eat solid food while having radiotherapy to the head and neck area. They will make sure you are having enough nutrition and calories each day. Some people need to be fed through a tube if they cannot eat and are losing lots of weight. This is known as artificial or tube feeding. It is only done for a short time until treatment is finished and your swallowing is back to normal.

Once your course of radiotherapy has finished, your mouth and throat slowly heal. Most people get back to eating normally after a few weeks. But it can sometimes take longer.

Radiotherapy to the head and neck often reduces the amount of saliva you make. Saliva washes your teeth and protects them from decay. So after radiotherapy, you are much more likely to get tooth decay.

You should see your dentist every 3 to 6 months and see a dental hygienist when your dentist suggests. Having regular check-ups means that if you develop any mouth problems, they can be picked up early when they are easier to treat. Your dentist or hygienist can give you a mouthcare routine you can follow to help prevent problems.

We have more information on looking after your mouth during treatment.

Tips for looking after your mouth and teeth

  • Brush your teeth or dentures with a small, soft toothbrush after each meal.
  • Use fluoride toothpaste and fluoride gel. The fluoride helps to protect and strengthen your teeth.
  • Rinse your mouth daily with a non-alcohol-based mouthwash, prescribed by your doctor.
  • You could try a salt mouth wash. Add 1 teaspoon of salt to 900ml of cooled, boiled water. You can use the mouthwash at least 4 times a day. After using it, rinse your mouth with cold or warm water. Make a fresh mouthwash each day.
  • Use dental floss or tape daily to clean between your teeth. If you are having chemotherapy or radiotherapy, check with your specialist doctor or nurse before doing this.
  • If your dentures are uncomfortable, you may need to leave them out for a few weeks.
  • Inspect your mouth daily for signs of infection – ask your dentist or specialist nurse what to look for.
  • Take sips of water and rinse your mouth regularly during the day to keep your mouth moist.
  • Only have sugary and acidic foods and drinks at mealtimes.
  • Do not smoke.
  • Do jaw exercises as advised by your specialist to prevent jaw stiffness.


Dry mouth

Radiotherapy can affect the salivary glands, so you may not make as much saliva as before. Your mouth and throat may become dry. This can make eating and speaking more difficult.

Sipping water regularly helps reduce the dry feeling, so carry a bottle of water with you. Eating soft, moist foods with gravy and sauces is easier than dry or chewy foods.

You may be prescribed artificial saliva to help your mouth feel more comfortable. It comes in different forms, such as sprays, gels, lozenges and pastilles. You may have to try different types to find one that works for you.

Some people find that using a humidifier in their home helps, as it makes the atmosphere less dry.

Your lips can also feel dry and chapped. You can keep your lips comfortable by using a lip balm regularly. But during radiotherapy, you should avoid products that are coloured, perfumed or flavoured.

After a few months, you may begin to make saliva again, but there may not be as much as before. Sometimes the salivary glands do not recover, which leaves the mouth permanently dry.

We have more information about coping with a dry mouth that you may find helpful.


Thick, sticky saliva (mucus)

Radiotherapy can change the consistency of your saliva. It may become thicker, stringy and sticky, like mucus. The mucus does not flow as well as normal saliva, so it may build up in the mouth and throat.

You may feel the need to spit frequently to get rid of the mucus build-up, so it is a good idea to keep tissues with you. Rinsing your mouth regularly can help. Using a sodium bicarbonate mouthwash every 3 to 4 hours may help clear thick saliva. To make the mouthwash, add 1 tablespoon of sodium bicarbonate to 900ml of cooled, boiled water. Rinse the mouthwash around your mouth and then spit it out. You should make a fresh mouthwash each day.

Alternatively, your specialist nurse can give you advice on the type of mouth rinse that might be best for you.

Sometimes a build-up of mucus can cause coughing, especially at night. Your nurse or doctor may prescribe nebuliser. This is a small machine that changes liquid medicine into a fine mist or spray, to help to loosen the mucus. If your sleep is disturbed by coughing, using a nebuliser before bed may help.

Changes in your saliva may get better within about 8 weeks of radiotherapy ending. But sometimes it continues for several months or longer. If the mucus continues, tell your cancer specialist or nurse. They may be able to prescribe medicines to reduce the amount you make.


Bad breath

Bad breath is usually caused by changes to your saliva and can be reduced by regular mouth care. It may also be caused by an infection in the mouth, which is common during radiotherapy treatment. If you have an infection, it can be treated with antibiotic or antifungal medicine.


Loss of taste

Radiotherapy to your head and neck affects your sense of taste. Some people lose their sense of taste completely or find that everything tastes the same (usually quite metallic or salty). Although your sense of taste should recover, it may take many months for this to happen.

We have more advice on coping with taste changes and other eating problems.

The most common question I’m asked is “When will I be able to taste food again?” I try to reassure them that their taste buds could come back. I can taste everything now that I could before.

Murray, hospital buddy for head and neck cancer patients


A hoarse voice

You may notice your voice becomes hoarse during treatment. If this happens, do not strain it. Try to rest your voice and avoid smoky atmospheres. A speech and language therapist (SLT) can give you more advice on what to do if your voice becomes hoarse. Your voice usually recovers after a few weeks.


Feeling sick (nausea)

Sickness is more likely to affect people who have combined chemotherapy and radiotherapy treatment. If it is a problem, your doctor can prescribe anti-sickness medicines (anti-emetics).

We have more information about controlling nausea and vomiting.


Tiredness (fatigue)

You are likely to become more tired as treatment goes on and have to take things slowly. Try to pace yourself and save your energy for things that you want to do or that need doing. Balance rest with some physical activity – even going for short walks will help you to feel less tired. Fatigue can continue for a few months after treatment finishes but slowly gets better.

We have more information about managing fatigue.

Back to Radiotherapy explained

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.

Before your radiotherapy

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

Your radiotherapy team

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