Side effects of radiotherapy 

Following radiotherapy, it's likely that you'll have some side effects. Side effects occur because radiotherapy temporarily damages some healthy cells, as well as destroying cancerous ones.

Side effects depend on:

  • the part of your body being treated
  • the dose of radiotherapy
  • how quickly the healthy cells are able to repair the damage

Radiotherapy affects different people in different ways and it's difficult to know exactly how you'll react to the treatment. For some people, side effects are mild, while others experience more severe effects.

Some side effects begin during treatment, whereas others can appear weeks or months afterwards.

Most side effects of radiotherapy only last for a few days or weeks after treatment has finished. However, some, such as tiredness or hair loss, can last a few months.

Before starting treatment, you should discuss the risks with your treatment team.

Common side effects

Most common side effects of radiotherapy are relatively mild and short-lived. Some are described below.

Sore skin

Your skin may become red and sore in the area being treated a few days or weeks into a course of radiotherapy, or for up to a couple of weeks afterwards.

Some people’s skin may peel (rather like sunburn). This usually heals within a couple of weeks.

Your treatment team will advise about the best way of caring for your skin during treatment. If your skin becomes sore, you should try not to irritate it further. For example:

  • avoid shaving and using perfumed soap in the affected area
  • protect your skin from cold winds and wear a high-factor sunscreen (SPF 15 or above) to protect your skin from the sun
  • use an electric razor instead of wet shaving
  • wear loose-fitting clothes made of natural fibres, and avoid tight collars, ties or shoulder straps
  • ask your treatment team about swimming in chlorinated water


You may feel tired both during and after radiotherapy. If you feel tired, make sure you give yourself time to rest, and take naps if necessary.

Tiredness is particularly common towards the end of a course of radiotherapy and can last for some time afterwards. Doctors believe it is due to the body repairing damage to healthy cells.

A shortage of red blood cells (anaemia) can also contribute to tiredness during radiotherapy. Therefore, blood tests may be required during radiotherapy for some cancers, to ensure you're not becoming anaemic. If you have anaemia, you may need a blood transfusion.

Feeling sick (nausea)

Most people aren't sick during radiotherapy. However, some people feel sick during, or for a short time after, their treatment. If you experience nausea, your doctor may be able to prescribe medication to help control it.

Radiotherapy to your abdomen (tummy area) or pelvic area may make you sick. This can last a few days after your treatment stops. Anti-sickness medication can be taken to help this.

Loss of appetite

The combination of feeling sick and tired during radiotherapy can make you lose your appetite.

If you have difficulty eating, you may find it easier to eat several small meals throughout the day. You can also speak to your radiotherapist, who may refer you to a dietitian (nutritional specialist).


Diarrhoea is a common side effect of radiotherapy to the abdomen or pelvic area. It usually starts a few days after treatment begins and gradually gets worse as treatment continues. Medication is available.

After your treatment has finished, diarrhoea should disappear within a few weeks. You should tell your doctor if your symptoms haven't improved after a few weeks, or if you notice any blood in your stools (faeces).

Hair loss

Hair loss is a common side effect of radiotherapy to your head or neck. Unlike chemotherapy, radiotherapy only causes hair loss in the area being treated.

Many people find losing their hair distressing and difficult to cope with. Talk to your family and friends about how you're feeling, so they can support you. Your treatment team may also be able to offer advice.

A few weeks after finishing treatment, your hair should start to grow back. In some cases, the hair grows back a different colour or texture to how it was before.

Read more about cancer and hair loss.

Discomfort when swallowing

Radiotherapy to the chest can cause the tube through which food passes (the oesophagus) to become temporarily inflamed, which may cause temporary discomfort when swallowing. If required, your doctor can prescribe medication to help soothe this.

You should avoid eating hot or spicy food and drinking acidic drinks or spirits during this time, because they can aggravate the problem.

Effects on sex and fertility in women

Having radiotherapy may cause you to temporarily lose interest in sex, particularly if you have other side effects, such as tiredness or nausea, or if you're anxious about your condition or treatment.

Radiotherapy to the vaginal area may cause your vagina to become sore and narrower. Your radiotherapist will tell you how to treat this using a vaginal dilator, which is a device inserted into your vagina to help prevent it narrowing. Having sex regularly after your treatment can also help to prevent your vagina narrowing.

If you experience vaginal dryness or pain when having sex, you can use lubricants or ask your GP or radiotherapist to prescribe appropriate medication.

If you have radiotherapy to the pelvic area, there's also a risk of infertility (see below).

Read more about the effects of radiotherapy on female sex and fertility on the Cancer Research UK website.

Effects on sex and fertility in men

In men, temporary erectile dysfunction and loss of interest in sex are common side effects of pelvic radiotherapy.

Read more about the effects of radiotherapy on male sex and fertility on the Cancer Research UK website.

Stiff joints and muscles

Radiotherapy can sometimes cause your muscles to tighten up and your joints to become stiff in the area being treated. You may also experience uncomfortable swelling in the affected area.

Exercising regularly can help to prevent stiffness. If you have stiff joints and muscles, your doctor or radiotherapist may refer you to a physiotherapist, who will recommend suitable exercises.

Read more about physiotherapy.

Long-term side effects

It's rare to develop severe, long-term side effects as a result of radiotherapy. Your doctor will discuss your chance of experiencing side effects before you consent to treatment.

Some possible long-term side effects are described below.

Infertility and early menopause in women

In women, radiotherapy to the pelvic area exposes the ovaries to radiation. In pre-menopausal women, this may cause early menopause (where a woman's monthly periods stop) and infertility (the inability to get pregnant). This is often very upsetting, particularly for younger women who want to have a family.

Before having treatment, your doctor will discuss all the options and available support with you. For example, it may be possible for some of your eggs to be surgically removed, frozen and stored until you are ready to have a baby.

However, this won't be possible if you need to have radiotherapy immediately, and it's not available on the NHS in all areas.

Infertility in men

Radiotherapy to the pelvic area or testicles can cause infertility in men, which may be temporary or permanent.

If there's a risk you could become infertile following radiotherapy, your doctor will discuss this with you before your treatment. It may be possible to store your sperm until you decide to have a baby, although this isn't always available on the NHS.

Changes to the skin

Long-term changes to the skin can occur after having radiotherapy. Some people notice that their skin is thicker, a slightly darker colour and, occasionally, dimpled (like the peel of an orange). These changes usually improve over time.

Bowel incontinence

Bowel incontinence, sometimes known as faecal incontinence, is a rare side effect of radiotherapy to the pelvis. It's the inability to control your bowel movements which can result in faeces (poo) leaking from your rectum (back passage).

Bowel incontinence can be treated with dietary changes, medicines or a number of different surgical procedures. Read more about treating bowel incontinence.


Radiotherapy can damage your body’s network of channels and glands that make up the lymphatic system. One of the functions of the lymphatic system is to drain excess fluid from your tissues.

If the lymphatic system is damaged, fluid can build up and cause pain and swelling. This is known as lymphoedema.

Lymphoedema often occurs in the arms or legs, although it can also affect other areas, such as the chest. Arm lymphoedema is sometimes seen in women who have had armpit surgery or radiotherapy for breast cancer.

It may be possible to prevent lymphoedema occurring using appropriate skincare techniques and exercise. If lymphoedema does develop, it can be controlled with early treatment in a specialised lymphoedema clinic.

Second cancer

Radiotherapy is sometimes associated with a slightly increased risk of developing certain types of cancer many years after treatment (called a "second cancer").

Page last reviewed: 01/04/2015

Next review due: 01/04/2017