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Side effects of cetuximab

Find out about the side effects of cetuximab.

Tell your doctor or nurse if you have any side effects so they can help you manage them. Your nurse will give you a contact number to ring if you have any questions or problems. If in doubt, call them.

Contact your doctor or nurse immediately if any of your side effects get severe or if you have signs of infection, including a temperature above 38C.

Common side effects

Each of these effects happens in more than 1 in 10 people (10%). You might have one or more of them.

You might feel very tired during your treatment. It might take 6 months to a year for your energy levels to get back to normal after the treatment ends. A low red blood cell count will also make you feel tired.

You can do things to help yourself, including some gentle exercise. It’s important not to push yourself too hard. Try to eat a well balanced diet.

Talk to your doctor or nurse if you are finding the tiredness difficult to manage.

This happens in 8 out of 10 (80%) of people having cetuximab. It may look like acne on your face, neck or trunk. Your skin might be dry and itchy. More than 1 in 6 people (15%) have a severe skin rash. 

The changes are usually very mild and unlikely to cause symptoms. They will almost certainly go back to normal when treatment is finished. 

You have regular blood tests throughout your treatment so your doctor can check this.

This happens in 3 out of 20 (15%) of people. Symptoms could be fever or chills. Paracetamol will help. 

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.

Talk to your doctor or nurse if you have this. 

Talk to your doctor or nurse if you have this. 

Talk to your doctor before starting treatment if you think you might want to have a baby in the future. 

A small number of people have an allergic reaction, usually during the first or second treatment.

Symptoms include a skin rash, itching, feeling hot and shivering. Other symptoms include redness of the face, dizziness, a headache, shortness of breath and anxiety.

Tell your nurse or doctor immediately if you have any of these symptoms.

Your nurse will keep a close eye on you and give you treatment straight away if this happens. They might slow your drip down.

Occasional side effects

Each of these effects happens in more than 1 in 100 people (1%). You might have one or more of them.

Signs of an infection include headaches, aching muscles, a cough, a sore throat, pain passing urine, or feeling cold and shivery.

Contact your treatment centre straight away if you have any of these signs or if your temperature goes above 38C. Severe infections can be life threatening.

Cancer drugs can reduce the number of white blood cells in the blood. This increases your risk of infections. White blood cells help fight infections.

Your white blood cell level begins to fall after each treatment. Then it gradually goes up again.

When the level is very low it is called neutropenia (pronounced new-troh-pee-nee-ah).

You have antibiotics if you develop an infection. You might have them as tablets or as injections into the bloodstream (intravenously). To have them into your bloodstream you need to go into hospital.

Cancer treatment can cause the level of red blood cells to fall (anaemia). This makes you breathless and look pale.

Red blood cells contain haemoglobin, which carries oxygen around the body. When the level of red blood cells is low you have less oxygen going to your cells.

You can also feel tired and depressed when your blood count is low and feel better once it is back to normal. The levels can rise and fall during your treatment. So it can feel like you are on an emotional and physical roller coaster.

You have regular blood tests to check your red blood cell levels. You might need a blood transfusion if the level is very low. After a transfusion, you will be less breathless and less pale.

Tell your doctor or nurse if you feel breathless.

You might notice you:

  • bruise more easily
  • have nosebleeds
  • have bleeding gums when you brush your teeth

This is due to a drop in the number of platelets that help clot your blood.

If your platelets get very low you may have lots of tiny red spots or bruises on your arms or legs called petechiae.

Tell your doctor or nurse straight away if you have petechiae.

You'll have a platelet transfusion if your platelet count is very low. It is a drip of a clear fluid containing platelets. It takes about 15 to 30 minutes. The new platelets start to work right away. 

You might have eye problems, including watery eyes and redness (conjunctivitis).

Let your doctor or nurse know if you have any problems with your eyes. They can give you eye drops to help.

This affects 1 in 20 people (5%).

This may be due to clouding of the lens of the eye (cataract), raised pressure in the eye, or damage to the optic nerve.

It is important to contact your doctor or specialist nurse as soon as possible if you have any of these symptoms. They may arrange for you to see an optician.

Tell your doctor or nurse if you have diarrhoea. They can prescribe medicine to help you. 

Drink at least 2.5 litres of fluid a day. This helps to keep you hydrated.

Ask your nurse about soothing creams to apply around your back passage (rectum). The skin in that area can get very sore and even break if you have severe diarrhoea.

Contact your doctor or nurse immediately if you have diarrhoea 4 or more times a day, or any diarrhoea at night.

Regular blood tests will check for this. 

You might lose your appetite for various reasons when you are having cancer treatment. Sickness, taste changes or tiredness can all put you off food and drinks.


  • Eating several small meals and snacks throughout the day can be easier to manage.
  • Ask your doctor or nurse to recommend high calorie drinks to sip between treatments, if you are worried about losing weight.
  • You can make up calories between treatments for the days when you really don’t feel like eating.
  • Drink plenty of fluids even if you can't eat.
  • Don't fill your stomach with a large amount of liquid before eating.
  • Try to eat high calorie foods to keep your weight up.

Feeling sick is usually mild. Anti sickness tablets can control it if you need them. Tell your doctor or nurse if you feel sick. 

Some people can have an allergic reaction while the treatment is going into their bloodstream.

Let your nurse or doctor know straight away if you have:

  • a sudden skin rash
  • itching
  • breathlessness
  • swelling of the lips, face or throat
  • feeling hot
  • shivering
  • redness of the face
  • dizziness
  • headache
  • anxiety
  • a sudden need to pass urine

Your chemotherapy nurse will keep a close eye on you and give you treatment straight away if this happens.

Rare side effects

Each of these effects happens in fewer than 1 in 100 people (1%). You might have one or more of them.

This can be caused by a build up of fibrous tissue (pulmonary fibrosis). Tell your doctor if you get a cough or breathless during or after your treatment. 

Blood clots can develop in the deep veins of your body. This is called deep vein thrombosis (DVT).

A DVT usually develops in the thigh or lower leg. A clot can block the normal flow of blood through the veins.

A blood clot can be very serious if it starts to move through your body. It can cause a blockage in your heart or lungs, although this isn’t common.

Treatment is with drugs to thin the blood.

Tell your doctor immediately if you have:

  • pain and swelling in one of your legs, usually at the back of your leg below the knee
  • warm, red skin in the affected area
  • shortness of breath
  • chest pain, which may be worse when breathing in

Talk to your doctor or nurse if you have this.

About cetuximab

More information about this treatment

We haven't listed all the very rare side effects of this treatment. For further information see the electronic Medicines Compendium (eMC) website.

You can report any side effect you have that isn’t listed here to the Medicines Health and Regulatory Authority (MHRA) as part of their Yellow Card Scheme.

Information and help

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