Side effects of radiotherapy for mouth and oropharyngeal cancer

Radiotherapy destroys cancer cells in a precise treatment area. But it also affects normal healthy cells within the treatment area. This can cause side effects. Knowing what to expect can help you to cope with them.

When do the side effects of radiotherapy start?

Side effects tend to start a few days after the radiotherapy begins. They gradually get worse during treatment. They can continue to get worse after your treatment ends. But they usually begin to improve 1 or 2 weeks after your treatment ends. Sometimes getting over a course of radiotherapy treatment can take several weeks or months. 

It’s important to avoid drinking alcohol and smoking during and after treatment. These can make the side effects worse. 

Everyone is different and the side effects vary from person to person. You may not have all of the effects mentioned.

Tiredness and feeling weak

You might feel tired during your treatment. It tends to get worse as the treatment goes on. You might also feel weak and lack energy. Rest when you need to.

Tiredness can carry on for some weeks after the treatment has finished but it usually improves gradually. Some people can feel very tired and exhausted. 

Various things can help you to reduce tiredness and cope with it, such as exercise. Some research has shown that taking gentle exercise can give you more energy. It's important to balance exercise with resting.

Feeling or being sick

You might feel sick at times. You can have anti sickness medicines. Let your treatment team know if you feel sick. 

Skin problems in the treatment area

Your skin might go red or darker in the treatment area. You might also get slight redness or darkening on the other side of your body. This is where the radiotherapy beams leave the body. 

The red or darker areas can feel sore. Your radiographers will give you advice on washing the area and creams to soothe your skin. The soreness usually goes away within 2 to 4 weeks of ending the treatment. But your skin might always be slightly darker in that area.

During your radiotherapy treatment, the skin might break down around the treatment area. Your nurse will use special dressings to cover and protect the area. The area usually heals up over a couple of weeks.

Tell the radiotherapy staff if you notice any skin changes

Mouth problems

Sore mouth and throat

Your mouth and throat might get sore. It may be painful to swallow drinks or food. You will have mouth washes to keep your mouth healthy.

You can have painkillers to reduce the soreness. Take them half an hour before meals to make eating easier.

Tell your doctor or nurse if your throat is sore.

Dry mouth

Your mouth might get very dry, which can be uncomfortable. Radiotherapy can damage the glands that produce saliva. Saliva is important for taste, swallowing, and speech. 

Various things can help:

  • Try to drink plenty of fluids if you can

  • Choose meals that are moist.

  • Use gravies and sauces to make swallowing easier.

  • Take regular sips of water with your meal to help you chew and swallow your food.

  • Suck small amounts of ice chips to refresh your mouth.

  • Chew sugar free chewing gum.

  • Ask your doctor about products that can stimulate saliva such as mouthwashes, gum, pastilles, and toothpaste.

  • Your doctor might prescribe artificial saliva and medicine to stimulate your salivary glands. 

  • It is very important to have regular check ups with your dentist.

Difficulty opening your mouth

Radiotherapy can damage the nerve that controls the muscles that move our mouth. This problem is called trismus. Your doctor or nurse will give you exercises to help strengthen your muscles.

Difficulty swallowing

During and after treatment, you might have difficulty swallowing.

You may see a speech and language therapist (SLT) before you start treatment if this is likely to affect your swallowing. An SLT can assess your swallowing during and after treatment. They can teach exercises to support you with swallowing difficulties. And they work with a dietitian if you are finding it difficult to eat.

You can have feeds through a nasogastric tube that goes up your nose and down into your stomach. Or you can have a PEG tube (percutaneous endoscopic gastrostomy tube) that goes through the skin into your stomach. Your nurse or dietician will tell you more about this if you need to have one. They will also show you and your relatives how to give the feeds. 

Tips for eating and drinking:

  • Drink about 3 litres of water a day while having treatment.
  • Eat soft foods.
  • Eat slowly and avoid eating late in the day.
  • Drink plenty during and after meals to soften your food.
  • Eat small amounts often rather than big meals.
  • Try different foods to find out which are easiest to swallow.
  • You can have high calorie drinks to boost your calorie intake if you need them.
  • You might need to have liquid food into your vein or through a tube into your nose or stomach if you can’t eat enough.

Hoarse voice

Your voice might become hoarse as you go through your radiotherapy. Depending on the treatment area your voice may disappear altogether. It will come back but may sound different afterward. 

Rest your voice from time to time and try not to strain it. You may find it helps to have a pencil and paper with you to write things down. Using your phone or computer tablet to write messages can also help. 

Changed sense of smell

Radiotherapy might affect your sense of smell. This is because radiotherapy causes dryness of the mouth and nose. If your nose is very dry you will not be able to smell things normally for a while. 

Taste changes

Your food may taste different. Some people often describe having a metallic taste, but others may lose their taste completely. This usually gets better a few weeks after your treatment has finished.  


  • Choose foods that have strong flavours, such as herbs, spices, marinades and sauces if all your food tastes the same.

  • Season your food with spices or herbs, such as rosemary, basil and mint.

  • Garnish cold meat or cheese with pickle or chutney.

  • Sharp tasting fizzy drinks such as lemonade or ginger beer are refreshing.

  • Some people find that cold foods taste better than hot foods.

Swelling (lymphoedema)

After radiotherapy to treat a head and neck cancer, you are at risk of getting swelling called lymphoedema in your neck or face. Lymphoedema is pronounced lim-fo-dee-ma.

Lymph fluid is in all body tissues. It comes from the tiny blood vessels into the body tissues. Usually, it drains back into the bloodstream through channels called lymph vessels. These are part of the lymphatic system.

A build up of lymph fluid in an area of the body can happen if lymph drainage channels or lymph nodes are blocked, removed, or damaged.

Lymphoedema in the head or neck can also cause symptoms inside your mouth and throat. For example, swelling of your tongue and other parts of your mouth.

Tell your doctor or nurse straight away if you:

  • have any swelling in the head or neck area or a feeling of fullness or pressure
  • find it difficult to swallow
  • have changes in your voice

Lymphoedema is easier to control if treated early. It's important that you are referred to a lymphoedema specialist if you have signs of swelling. This is usually a nurse or physiotherapist.

Unfortunately, it is not possible to cure lymphoedema. But things can be done to reduce the swelling and help you feel better. For example, positioning and lymphoedema exercises can help.

Hair loss in the treatment area

Radiotherapy causes hair loss in the area of treatment. It may also cause hair loss where the radiation beam leaves the body (the exit site). 

It usually starts to grow back a few weeks after treatment. Ask your radiotherapy team to show you where you will lose your hair.

Damage to the jawbone 

Radiotherapy can sometimes damage the jawbone and break down the bone. This is because radiotherapy can reduce the blood supply to the bone. This is called osteoradionecrosis. This is rare but it can happen months or years after your treatment has finished. Symptoms include pain and swelling in your gums.

Before your radiotherapy, you usually see a specialist dentist. They can remove damaged or broken teeth and make sure your dentures fit properly. 

They will also show you how to keep your mouth and teeth clean. You will need to do this during your radiotherapy and for a few months afterward, or sometimes longer. 

Side effects if you have chemotherapy with radiotherapy

Chemotherapy combined with radiotherapy can make some side effects worse. Combining these treatments is called chemoradiotherapy.

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Last reviewed: 
14 Jun 2022
Next review due: 
14 Jun 2025

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