Possible side effects

Some side effects may affect you no matter which area of the body you’re having radiotherapy to. It’s important to remember that most people will have a few side effects and they will often be mild. Most people only experience a few of the following:

  • tiredness
  • feeling sick
  • skin reactions
  • hair loss.

There are ways to help you manage side effects so they’re easier to cope with. If you need help and advice about dealing with any, speak to your doctor or radiotherapy staff. Most side effects last for about 10-15 days after treatment finishes.

Some people have side effects that last for longer, or develop a while after they have finished their treatment. These are called long-term or late effects.

Before you have radiotherapy, your clinical oncologist will talk to you about any likely side effects. You can ask the oncologist about any you’re particularly worried about.

Side effects of radiotherapy

You may develop side effects over the course of your treatment. These usually disappear gradually over a few weeks or months after treatment finishes. Your doctor, nurse or radiographer will discuss this with you so you know what to expect. Let them know about any side effects you have during or after treatment, as there are often things that can be done to help.

It’s not unusual to feel worse before you start to feel better. Some people can find this a very difficult time, and they may feel low or even depressed for a while. Your clinical oncologist can advise you about what to expect.

Radiotherapy does not make you radioactive and it’s perfectly safe for you to be with other people throughout your treatment, including children and pregnant women.


Not everyone feels tired during radiotherapy treatment but many people do. For example, some people are able to continue working, but others need to take time off work.

Tiredness (fatigue) can continue for weeks to months after your treatment has finished. It can often be made worse by having to travel to hospital each day, or by other treatments such as surgery or chemotherapy.

Managing tiredness

Get plenty of rest but balance this with some gentle exercise, such as short walks. This will give you more energy and help to keep your muscles working. Save some energy for doing the things you enjoy and ask others for help doing chores if these are tiring you out.

We have more information about coping with fatigue.

Feeling sick

Some people find that their treatment makes them feel sick (nausea), and sometimes they may actually be sick (vomit).

This is more likely to happen if the treatment area is near the stomach, or if the brain is being treated.

Your clinical oncologist (or sometimes a nurse or radiographer) can prescribe anti-sickness (anti-emetic) drugs if this happens. They may also prescribe them as a precaution. Tell your clinical oncologist or specialist radiographer if you have any nausea or vomiting, and remember that it usually stops once treatment is over.

Managing sickness

You may find it helpful to let someone else cook or prepare food for you, especially if the smell of cooking makes you feel sick. Sipping a fizzy drink slowly through a straw, drinking ginger tea, or eating crystalised ginger or ginger biscuits can also help.

If you’re given anti-sickness tablets, take them regularly, as this is the best way to control any sickness. Some anti-sickness medicines work best if you take them before your radiotherapy treatment. Ask your doctor, radiographer or nurse to tell you the best time to take your anti-sickness medicines.

We have more information to help you cope with feeling and being sick.

Skin reactions

You may develop a skin reaction while having external radiotherapy. If this happens, it usually begins after about 10 days.

How your skin reacts will vary depending on the amount of radiotherapy you have. Some people may find that the skin in the treatment area becomes red and sore or itchy. Or, it may become darker with a blue or black tinge. Sometimes the skin will get very sore and it may break and leak fluid, although this doesn’t happen very often. If your skin gets very sore, your treatment may have to be delayed for a short time to allow the area to recover, although this is very rare.

If you have a skin reaction, it will usually settle down 2–4 weeks after your treatment has finished. But the area may stay slightly darker than the surrounding skin.

Managing skin reactions

During your treatment, you will usually be advised to:

  • wear loose-fitting clothes made from natural fibres, such as a cotton T-shirt
  • wash your skin gently with soap, or aqueous cream, and water and gently pat it dry (aqueous cream should not be used as a moisturiser)
  • avoid rubbing the skin
  • avoid heating and cooling pads
  • avoid shaving, if possible
  • not use hair-removing creams or products, including wax
  • use a moisturiser that is sodium lauryl sulphate-free (your radiographer can give you more information about this)
  • use normal deodorant, unless your skin is broken
  • avoid the sun and use a high sun protection factor (SPF) sunscreen (your radiographer can give you more information about this).

If you develop a skin reaction such as soreness or a change in skin colour, let the radiotherapy staff know as soon as possible. They will advise you on the best way to manage it.

After your treatment has finished, you’ll need to protect the skin in the treated area from strong sunshine for at least a year.

Once any skin reaction has settled down, you should use a suncream with a high SPF of at least 30.

You should also wear close-weave clothing and a wide-brimmed hat if your head and neck area has been treated. It’s important to remember that you can burn through clothing if you’re out in hot sun for a long time. Your radiographer can give you more information about this.

You can usually go swimming once any skin reaction has settled down. This is usually within a month of finishing treatment. Remember to use a waterproof suncream if you’re swimming outdoors.

Hair loss

Radiotherapy will only cause hair loss in the treatment area.

Hair loss can also happen where the radiation beam leaves the body (for example, on the back of the neck), as well as where it enters the body. Ask your clinical oncologist or radiographer to show you exactly where your hair is likely to fall out.

Hair usually begins to fall out 2–3 weeks into radiotherapy treatment. It usually grows back after treatment finishes, but it may be a different texture or colour than before. It may take several months to grow back, although it depends on the dose of radiotherapy you have.

Occasionally, hair loss is permanent. Your doctor or radiographer can tell you if any hair loss is likely to be permanent.

Managing hair loss

If you lose the hair on your head, you may want to wear a wig to cover up your hair loss. Other ways of covering up hair loss include wearing a scarf or turban.

We have more information to help you cope with hair loss.

Long-term or late side effects of radiotherapy

All cancer treatments can result in long-term side effects. Modern ways of giving radiotherapy aim to limit the risk of permanent side effects. This has meant that the number of people who develop long-term problems is reducing. However, when radiotherapy is also given with chemotherapy, the long-term effects of radiotherapy may be increased.

Before you consent to the radiotherapy, your clinical oncologist will discuss the likelihood of you developing long-term side effects. It’s important that you have the opportunity to talk these through with your oncologist, even though they might not happen to you.

Second cancers

Radiotherapy can cause cancer, and a small number of people will develop a second cancer because of the treatment they've had. However, the chance of a second cancer developing is so small that the risks of having radiotherapy are far outweighed by the benefits.

If you’re concerned about your risk of developing a second cancer, talk to your cancer specialist.

Back to Radiotherapy explained

Before your radiotherapy

Before you start radiotherapy, your team will explain what your treatment involves and how it may affect you.

Your radiotherapy team

You will meet many different specialists from your radiotherapy team. You may see them before, during and after radiotherapy treatment.