Side effects of radiotherapy

Radiotherapy for anal cancer can cause side effects. Some possible side effects are:

  • tiredness
  • effects on the skin
  • bladder changes
  • bowel changes
  • feeling sick
  • hair loss.

Many side effects can be managed successfully and most will begin to get better a few weeks after treatment ends.

Some people may 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.

Your cancer specialist, specialist nurse or radiographer will explain the most likely side effects in your situation. Always tell them about any new symptoms. They will be able to suggest ways of managing them and tell you about treatments that can help.

Possible side effects during treatment

During treatment, you may have some of the side effects explained in this information. It’s important to tell your radiographer, cancer specialist or specialist nurse if you do. They can give you advice on how to manage them and tell you about the treatments that can help.


Radiotherapy often makes you feel tired, especially towards the end of the course of treatment. The tiredness (fatigue) continues after the treatment has finished and may last for a few months. You’ll find that your energy levels will gradually improve. However, it can take a while to recover, so don’t be too hard on yourself.

There are some things you can do to help manage tiredness:

  • Pace yourself so you don’t overdo it and take regular rests.
  • If you’re able to, plan some physical activity into your day, such as a short walk. This will help to build up your energy levels.
  • Ask family and friends to help out, perhaps with things like household tasks and taking care of children.
  • Make sure you get enough sleep.

Effects on the skin

Sometimes, radiotherapy can cause a skin reaction in the area being treated. The skin may redden or get darker and become dry, flaky and itchy. Towards the end of treatment, the skin sometimes becomes moist and sore. There may be breaks in the skin, especially around the back passage (anus) and groin.

Your radiographer or nurse will check your skin regularly. Tell them if your skin is sore or if you notice any other changes. They will assess your skin and may prescribe a cream or dressings to help. They can also prescribe painkillers, if needed.

Skin reactions may be at their worst up to two weeks after radiotherapy finishes, before beginning to improve. If you’re sore or have any problems with your skin during this time, contact the radiotherapy department for advice.

Pelvic radiotherapy may make the hair around your genital area (pubic hair) fall out. It should start to grow back again within a few weeks after radiotherapy finishes, but it may be thinner. Occasionally, hair loss can be permanent.

Skin care

Your radiographer or specialist nurse will tell you how to look after the skin in the treated area. They will usually give you the following advice:

  • Keep the skin in the area clean. Wash it gently and carefully pat it dry with a clean, soft towel.
  • Check with the radiographer or nurse before you put anything on the skin in the treated area.
  • It is better to have a shower than take a bath, as soaking in a bath can make the skin too moist. When having a shower, use a very gentle stream of lukewarm water. If you have a bath, don’t soak in the water for longer than a minute or two.
  • Use a simple moisturiser on the skin. Your radiographer or specialist nurse will be able to suggest moisturisers you can try.
  • Wear loose underwear made from natural fibres, such as cotton or silk, that won’t rub against the skin. Avoid wearing tights or tight-fitting trousers.
  • If you shave, wax or use hair removal creams, wait until a few weeks after radiotherapy is over and any skin reaction has healed.
  • Protect the skin in the treatment area from the sun for the first year after radiotherapy. Even after any skin reaction has settled, you should always wear sunscreen with a high sun protection factor (SPF) of at least 30.
  • Wash your underclothes, bed linen and towels using a non-biological powder or liquid for people with a sensitive skin.
  • Avoid smoking, as this can make skin reactions worse.

Bladder side effects

Pelvic radiotherapy can cause irritation and inflammation of the lining of the bladder. You may find that you have some of the following symptoms:

  • a need to pass urine often (frequency)
  • a need to pass urine during the night (nocturia)
  • a burning sensation when you pass urine (similar to cystitis)
  • a feeling that you can’t wait when you find you need to empty your bladder (urgency)
  • blood in your urine (haematuria)
  • leaking small amounts of urine (incontinence).

Your doctor can prescribe painkillers or anti-inflammatory drugs to ease these symptoms. A sample of your urine may be tested to make sure there’s no infection present. If you have an infection, your doctor will prescribe a course of antibiotics for you. There are also things you can do to help with these symptoms.

What you can do

  • Drink at least 2–3 litres of fluid a day – urine that’s concentrated irritates the bladder and makes symptoms worse, so drinking more reduces this.
  • Avoid smoking, which can make the symptoms of bladder irritation worse.
  • Avoid drinks that can irritate the bladder. These include drinks containing caffeine (tea, coffee, cocoa and cola), alcohol, fizzy drinks, acidic drinks (fresh orange and grapefruit juice) and drinks with artificial sweeteners (‘diet’ or ‘light’ drinks).
  • Let your nurse or radiographer know if you leak urine (incontinence).
  • If symptoms get worse, you have a high temperature, or you feel you can’t pass urine, contact the hospital straight away.

If you have incontinence, your nurse will take a urine sample to check for signs of infection. This is a common and easily treatable cause of incontinence. They may also arrange for you to have pads if needed and give you advice on looking after your skin. If the problem doesn’t settle within a few weeks, they can refer you to a continence specialist for advice and treatment.

Just Can’t Wait toilet card

If you need to go to the toilet more often, or feel that you can’t wait when you do want to go, you can get a card to show to staff in shops, pubs and other places. The card allows you to use their toilets without them asking awkward questions.

You can get a card from the Bladder and Bowel Foundation.

Bowel side effects

Pelvic radiotherapy can cause some of the following side effects:

  • loose stools, diarrhoea or sometimes constipation
  • a need to open your bowels urgently
  • cramping pains in your tummy (abdomen) or back passage
  • passing a lot of wind.

Some other, less common side effects are:

  • feeling as if you need to go to the toilet although your bowel is empty (tenesmus)
  • passing mucus or blood when you empty your bowels
  • slight soiling of your underwear or some leakage (incontinence), although this is rare.

Tell your cancer specialist, specialist nurse or radiographer about any bowel side effects you have.

Diarrhoea is the most common side effect and usually starts during or after the second week of radiotherapy. If you have diarrhoea, your specialist will prescribe anti-diarrhoea tablets to help reduce it.

Some people are advised to make changes to their diet during radiotherapy. This may involve eating a bland diet and cutting down on fibre. Your specialist nurse or radiographer will tell you if this is appropriate for you. If you have diarrhoea, you should drink plenty of fluids.

If you have tummy cramps, tell your cancer specialist or nurse. They can prescribe drugs to help with this. If you’re constipated, your doctor will usually prescribe a laxative and give you advice on diet.

Let your nurse or radiographer know if you have any soiling or leakage. They will give you advice on coping with this and looking after the skin in the area.

Bowel side effects usually start to improve about two weeks after radiotherapy has finished. Sometimes, it may take a few months for the bowel to settle down.

What you can do

  • Drink at least 2–3 litres a day (to replace fluid lost through diarrhoea) and avoid caffeine and alcohol.
  • Follow any dietary advice given by the hospital.
  • Take your anti-diarrhoea tablets or other medicines you have been prescribed.
  • Avoid foods and drinks that give you wind, such as pickles, beans, curry and fizzy drinks.
  • Gentle exercise may help if you have a lot of wind. Or you could try charcoal tablets, which you can buy at the chemist.
  • If side effects don’t get better, tell your specialist nurse or doctor.
  • Avoid smoking, which stimulates the bowel and can make diarrhoea worse.

There is more information about coping with bowel problems in our section on eating problems and cancer.

Toilet card

If you need to go to the toilet more often, or feel that you can’t wait when you do want to go, you can get a card to show to staff in shops, pubs and other places. The card allows you to use their toilets without them asking awkward and embarrassing questions.

Macmillan produces this toilet card. We hope this card helps you get urgent access to a toilet, but we cannot guarantee that it will work everywhere.

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.

Hair loss

It’s common to lose your pubic hair. It should grow back after your treatment finishes, although hair loss may be permanent.

These side effects usually decrease gradually once the treatment has ended, but it may take some months for skin changes to go back to normal. It’s important to discuss any problems with your doctor or specialist nurse, as there are often ways to reduce them.

We have more information about coping with hair loss.

Possible long-term side effects

Newer ways of giving radiotherapy aim to reduce 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 given with chemotherapy, the long-term effects of radiotherapy may be increased.

We have more information about coping with late effects of radiotherapy.

Back to Pelvic radiotherapy explained

Fertility and pelvic radiotherapy

Pelvic radiotherapy can affect your fertility. This can be distressing but getting the right support can help you to find ways of coping.