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.

Your clinical oncologist (or sometimes a nurse or radiographer) can prescribe very effective anti-sickness (anti-emetic) drugs if this happens, and they may prescribe them anyway 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 can help with feelings of sickness. Or try crystalised ginger, ginger tea or ginger biscuits. If you’re given anti-sickness tablets, take them regularly, as this is the best way to keep the sickness controlled. 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 about coping with nausea and vomiting.

Skin reactions

Some people develop a skin reaction while having external radiotherapy. If this happens, it may begin 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. 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 rare.

The extent of the reaction depends on the area being treated and your skin type. Some people have no skin problems at all. If you have a skin reaction, it will usually settle down 2–4 weeks after the treatment has finished, but the area may stay slightly darker than the surrounding skin.

Managing skin reactions

During your treatment, you should avoid using any deodorants, soaps, perfumes and lotions on your skin other than those advised by the radiographers. 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 treatment 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 sun protection factor (SPF) of at least 30. You should also wear close-weave clothing and use 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. 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.

Clothes can sometimes irritate the skin or cause discomfort in the area being treated. Wearing loose-fitting clothes, preferably made of natural fibres rather than man-made materials, can help. You should also avoid wearing tight collars and ties if you’re having radiotherapy to your neck. Bra and handbag straps can cause irritation if they rub against treated skin. If your chest area is being treated, you may be more comfortable not wearing a bra or wearing a vest instead.

We have more information about coping with skin problems.

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 will fall out.

Hair usually begins to fall out after 2–3 weeks. Hair should grow back after treatment finishes. This may take several months, although it depends on the dose of radiotherapy you have. Occasionally, hair loss is permanent. Your 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 or cover up in other ways. We have more information about hair loss, which gives helpful tips on what you can do to cover up and how to cope with the emotional effects.

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

Who might I meet?

You will meet many different specialists before, during and after radiotherapy treatment.