Possible side effects of radiotherapy

Your specialist will explain the most common side effects 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’ll usually find the side effects have improved a lot within 6–8 weeks of radiotherapy finishing. Some 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.

If your mouth and throat are sore, your specialist can prescribe painkillers to control this. A dry mouth and loss of taste can sometimes take months to recover. There are different things that you can do to help this.

Your specialist will explain if your treatment may cause any long-term effects. Radiotherapy reduces the amount of saliva you produce. Because saliva protects your teeth from decay you’ll 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 troublesome, depending on the dose of radiotherapy 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 two weeks of radiotherapy. They may continue to affect you for 7–10 days after treatment ends before gradually improving. Most people find that side effects have noticeably improved 6–8 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’s 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. You’ll also be told about things you can do to help reduce the risk of having problems.


Sore and sensitive skin

The skin over your face and neck will gradually redden or darken and may feel sore and itchy (a bit like sunburn). This starts after about two weeks of treatment and lasts for up to about four weeks after radiotherapy has finished.

The radiotherapy team will advise you on how to look after your skin. It’s very important to use only the soaps, creams and lotions that they recommend, as chemicals in some products can make the skin more sensitive to radiation. It’s 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’s 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. But don’t use sun protection creams on your head and neck while you’re having radiotherapy. The radiotherapy team can talk to you about when and how to use sun protection cream after your treatment.


Sore mouth

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

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

Once your course of radiotherapy has finished, your mouth will gradually heal and most people get back to eating normally after a few weeks.

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’ll be much more likely to get tooth decay.

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


Loss of taste

If you have radiotherapy to your head and neck, it will affect 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 information on coping with taste changes and other eating problems.


A hoarse voice

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


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 – carry a bottle of water with you. Soft, moist foods with gravy and sauces will be easier to eat 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 and lozenges. You may have to try different types to find one that suits 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 you should avoid products that are coloured, perfumed or flavoured during radiotherapy.

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


Thick, sticky saliva (mucus)

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

You may feel the need to spit frequently to get rid of the mucus build-up, so it’s a good idea to keep tissues handy. Rinsing your mouth regularly can help to cut through the mucus. You can make a mouth rinse with half a teaspoon of salt and half a teaspoon of baking soda mixed into a litre of water. Alternatively, your specialist nurse can give you advice on the type of mouth rinse that’s suitable for you.

Sometimes a build-up of mucus can cause coughing, especially at night. Your nurse or doctor may prescribe nebulisers (a liquid that is mixed with air to make a mist or fine 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 eight weeks of radiotherapy ending but sometimes continue for several months or longer. If the mucus continues, there are medicines that can be prescribed to reduce the amount you make. Tell your cancer specialist or nurse if you’re having difficulties.


Bad breath

This 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 your mouth, which is common during radiotherapy treatment. If you have an infection, it can be treated with antibiotic or antifungal medicine.


Feeling sick (nausea)

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


Tiredness (fatigue)

You’re likely to become tired and have to take things more 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 just going for a short walk will help increase your energy.

Back to Radiotherapy explained

Planning your treatment

Your radiotherapy will be carefully planned. You’ll have a special mask made to keep your head still during treatment.

Who might I meet?

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