Side Effects Of Radiation Therapy

  • Agnes ChanBSc Cognitive Neuroscience and Psychology, University of Manchester
  • Pranjal YeoleBachelor's of Biological Sciences, Biology/Biological Sciences, General, University of Warwick, UK

Have you ever heard of radiation therapy? You probably have but do you know what its side effects are? This article will provide you all you need to know about the side effects of radiation therapy.

Common side effects are fatigue, skin problems and hair loss. However, depending on which part of the body is treated, patients may experience different side effects, such as nausea and vomiting, sexual problems and throat problems.

Want to know more about the side effects of radiation therapy? Keep scrolling and read on!


Radiation therapy is used to kill cancer cells and shrink tumours with radiation in the early stages of cancer, which mostly occurs in a hospital setting. 

There are various types of radiation therapy:

  • Curative radiation therapy: it attempts to cure the cancer completely. 
  • Neo-adjuvant radiation therapy: it helps increase the effectiveness of other treatments such as chemotherapy.
  • Adjuvant radiation therapy: it aims to reduce the chance of cancer coming back after surgical operation. 
  • Palliative radiation therapy: it plays a role in relieving symptoms in situations where there is not a cure for the cancer.

Radiation therapy can be given in the following ways:

  • External radiation therapy: beams of radiation aimed at the cancer using a machine.
  • Brachytherapy: also known as radiation therapy implants. Small pieces of radioactive metal will be put close to the cancer inside your body.
  • Radioisotope therapy: radioactive liquid being put inside your body through injections into your blood, capsules or drinks.
  • Intrabeam radiation therapy: during breast cancer surgery, radiation will be delivered at the tumour directly. 

Side Effects


People taking radiation therapy often feel tired physically, mentally and emotionally. You might feel extremely tired and lacking energy. It is described as feeling very weak, listless or drained. Some may find themselves too tired to do simple everyday activities like eating, walking to the bathroom and using the TV remote. It is very common among cancer patients and usually occurs after the first few weeks of radiation therapy as both healthy and cancer cells are being destroyed. Most of the time, fatigue gets worse as you go on with the treatment. The fatigue you feel from having radiation treatment is not the same as the fatigue from daily life. It can interfere with your daily activities. You might not feel better after getting some rest. Fatigue can be more distressing than other side effects of radiation therapy like nausea and vomiting. It can last long but it usually goes away a few months after your treatment ends. 

Ways to manage fatigue:

  • Go for a walk
  • Do yoga
  • Plan time to rest by taking short breaks between activities
  • Keep a record of your feeling every day to better plan out what the best way is to spend your time
  • Talk to your doctor or nurse about your changes in energy level 
  • Eating several small meals instead of three large ones
  • Drink plenty of fluids

Skin Changes

Skin changes include dry skin, itchy skin, blistering skin and peeling on the skin. This is called radiation dermatitis. These side effects often appear 1 to 2 weeks after the start of treatment and go away after the end of the treatment. However, for some people, the affected area of the skin may look darker and be more sensitive than before. You can do the following to care for your skin: 

  • ​​Wash your skin daily with a body wash of your choice
  • Do not rub your skin to dry it, pat it instead
  • Moisturise your skin daily with a moisturiser
  • Use the deodorant that you have been using, use another one if it irritates your skin
  • Avoid shaving the area of the skin that has problems
  • Avoid using heat packs and cold packs on the affected area
  • Wear clothes that are more loosely fitted and made from natural fibres
  • Avoid tight bands, ties and straps on the affected area
  • Use a sunscreen that has a SPF 50 or above for protection from the sun. Keep using it for at least a year after your treatment finishes
  • Ask your doctor and nurse whether you can continue swimming as chlorine in the water may be bad for your skin problems 
  • If your skin breaks, stop putting on the products that you have been using on your skin

Hair Loss (Alopecia)

Hair loss is fairly common in cancer patients undertaking radiation therapy. It only causes hair loss in the area being treated with radiation. It usually starts within 2 to 3 weeks after treatment begins. Your hair will usually grow back in a few weeks of time after your treatment ends although its texture and colour might change compared to before the treatment. There are several things you can do to manage hair loss

  • Treat your hair gently
  • Cut your hair short or even shave your head before treatment starts
  • Getting a wig
  • Wearing a scarf or turban
  • Protect and care for your scalp with sunscreen, wearing a hat or a scarf
  • Talk about your feelings with someone who understands and close family members

Feeling sick

In some patients, they may feel sick during or after sessions of radiation therapy. It is more common for those who have radiation therapy near their stomach, like the gastrointestinal tract and liver, or in the brain. This feeling should stop after the treatment finishes. There are ways to manage the feeling of nausea and vomiting, such as taking anti-nausea medicine, drinking plenty of water and fluids, and avoiding greasy, fried, sweet or spicy food.

Low blood count

Changes in blood count levels due to radiation therapy are rare yet possible. As these blood cells play an important role in fighting infection and preventing bleeding, if you have low blood counts after taking radiation therapy, you may need to stop taking the treatment for about a week, so that your blood count level can return to normal levels. 

Changes in appetite 

Some patients may experience sore mouth, loss of appetite, weight loss and discomfort when swallowing. 

Sore mouth

Radiation therapy to the head and neck may cause soreness and irritation to the lining of the mouth (mucositis). It usually appears a few weeks after the therapy begins. You may feel soreness on the inside of your mouth similar to the feeling of being burned by hot food and drink. You may also have mouth ulcers, dry mouth, reduced sense of taste and bad breath. These symptoms will make you feel uncomfortable when eating, drinking and talking. If you experience sore mouth, you should avoid spicy, salty and sharp food. Your doctor may suggest painkillers or mouthwash that could help alleviate the soreness.

Loss of appetite

As radiation therapy takes up a lot of your body’s energy to heal, you may find yourself losing your appetite. Sometimes there can be a change in the sense of taste. However, it is important to maintain a healthy diet throughout radiation therapy with enough calories, protein and fluids. If you find yourself losing your appetite, you can try the following ways to increase your appetite:

  • Eat slowly
  • Eat more when you feel good
  • Have meals with someone you like spending time with
  • Prepare foods that are easy to make for the times when you have low energy

Discomfort when swallowing

Radiation therapy to the head and neck may have negative impacts on your salivary glands and tissues in your mouth. This makes it more difficult for you to chew and swallow safely. Foods that are soft, wet and easy to swallow are preferable in this situation. You can soften foods with sauce or other liquids. You can also make milkshakes and smoothies as these are easier to swallow. Crunchy, salty, spicy and sugary foods and drinks are not recommended as they irritate your mouth. Alcohol and tobacco products should also be avoided. Talk to your doctor if you feel like painkillers or other pain medicine would be helpful. 

Long-term side effects

  • Change in skin colour
  • Red spider marks on the skin
  • Dry mouth
  • Breathing problems
  • Chances of infertility
  • Low sex drive
  • Impotence
  • Soreness and pain
  • Changes in bowel
  • Inflammation in bladder
  • Swelling due to blocked drainage channels to the arms or legs (lymphoedema)

Side Effects Based on Treatment Area


  • Fatigue
  • Hair loss
  • Memory or concentration problems
  • Nausea and vomiting
  • Skin changes
  • Headache
  • Blurry vision
  • Trouble with memory and speech
  • Seizures 
  • Hearing loss


  • Fatigue
  • Hair loss
  • Skin changes, including feeling tender or sensitive to touch and darker skin
  • Swelling of the breast
  • Trouble moving your arm and shoulder


  • Fatigue
  • Hair loss
  • Skin changes
  • Throat problems, like having trouble with swallowing
  • Cough
  • Shortness of breath

Head and neck

  • Fatigue
  • Hair loss
  • Mouth problems 
  • Skin changes
  • Taste changes
  • Throat problems
  • Less active thyroid gland


  • Diarrhoea
  • Fatigue
  • Hair loss
  • Nausea and vomiting
  • Sexual problems 
  • Fertility problems
  • Skin changes
  • Urinary and bladder problems


  • Diarrhoea
  • Fatigue
  • Hair loss
  • Sexual problems
  • Fertility problems
  • Skin changes
  • Urinary and bladder problems

Stomach and abdomen

  • Diarrhoea 
  • Fatigue
  • Hair loss
  • Nausea and vomiting
  • Skin changes
  • Urinary and bladder problems


Radiation therapy can be very distressing as it has lots of side effects, such as fatigue, hair loss and skin problems. Although some may even last longer after treatment ends, like dry mouth and darker skin, most of the side effects disappear as treatment ends. Radiation therapy remains a very common and effective treatment for cancer. If you have any concerns about radiation therapy, you should consult your doctors so that they can make the treatment plan that best suits your needs. 


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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Ka Yin Chan

BSc Cognitive Neuroscience and Psychology, University of Manchester

She is a Neuroscience student with strong interest in clinical research and medical communications. She believes that the ever-growing field of scientific research is crucial for understanding health and hence improve it.

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