Side effects of radiation treatment

Also called radiotherapy or radiation therapy

Radiation therapy side effects depend on the part of your body being treated.

On this page, you can find the following information:

Not everyone has the same reaction to radiation treatment. Side effects depend on the amount of radiation given, the area of the body treated, the type of radiation used and the individual response. Other side effects can include tiredness, changes to the skin, hair, appetite, bladder or bowel, mouth and throat, lymph nodes and sexual functioning.

Side effects may be acute or late

Side effects of radiation treatment are commonly grouped into those that develop early on, during, or at the end of the treatment (the acute side effects); and those that develop many months, if not years, later (late side effects).

Acute side effects

The inflammation caused by the radiation beams passing through normal tissue results in the acute side effects. These side effects peak about a week after the treatment has finished. Most side effects will be greatly improved by about 6 weeks after the treatment has finished. Your doctor will tell you what you are likely to experience.

Late side effects

Late side effects appear many months or years later. The inflammation of the tissues will have settled. Sometimes the initial damage and this healing process might result in scarring and damage to these tissues, which will restrict their function. Your treatment will have been planned specifically to minimise the likelihood of late complications and any significant risks that might exist will be discussed with you.

Feeling tired

Fatigue/tiredness is a major side effect of radiation treatment. If you do get tired try to take things easier. Only do as much as you feel comfortable doing. Try to plan rest times in your day. Drinking plenty of fluids, eating well and having some form of physical activity will help you cope better with treatment.

If you are not sleeping well, tell your treatment team. They might be able to suggest ways to help, or prescribe sleeping tablets or a mild relaxant.

Effects on the skin

The skin in the treatment area may become dry, flaky, red, itchy or sore, similar to sunburn. It depends on the amount of radiation the skin receives.

Your skin may also be more sensitive than usual to the sun, so try to keep treated areas out of the sun during and after treatment. Once the reaction improves, ask your doctor about using a sunscreen (SPF 30+).

Skin care

  • Wear soft, loose clothing.
  • Tell your treatment team about changes in your skin, such as cracks, blisters, very moist skin, rashes, infections or peeling, or any changes in your nails.
  • Do not rub, scrub or scratch treated skin or any sensitive spots.
  • Follow skin care advice given by your treatment team, eg, avoid using soap, perfume, deodorant on treated areas; use a soft towel; bath or shower as usual in warm water.
  • Do not put hot-water bottles or ice packs on treated areas.
  • If skin becomes sore, only use products recommended by the treatment team.

Hair loss

You may lose some or all of your hair in the treatment area, e.g. scalp, chest, face. This may be temporary or permanent.

If you have lost, or are losing your hair you could consider wearing a wig, hair piece, hat or scarf for a while. If you decide to wear a hair piece or wig, it is a good idea to get one fitted before you start losing your hair, so that it matches as closely as possible your style and colour. The Ministry of Health helps pay the cost of a hair piece, wig or hair covering. Ask your doctor for a certificate that states your entitlement.

Not wanting to eat

Your appetite might be normal during treatment, or you may not feel like eating at all. Your sense of taste may change, especially if you have had treatment to your head and neck.

Eat as well as possible during your treatment to keep your strength up and avoid weight loss. Try different foods until you find foods that appeal. Eat smaller amounts more often, or try drinking special liquid supplement foods that you can get from your pharmacist. Even when you are unable to eat very much, it is important to drink plenty of clear fluids.

Your hospital may have its own diet information for cancer patients. You can also talk to the hospital or community dietitian for advice about what to eat. Also see: Eating well when you have cancer

Feeling sick and diarrhoea

Feeling sick, diarrhoea and vomiting might happen if you are having radiation to the oesophagus (gullet), stomach, bowel, brain, or pelvic area. Your radiation oncologist can prescribe medication to help relieve these symptoms. Maintaining a good fluid intake is important.

Bladder and bowel irritation

Bowel problems resulting from pelvic radiation treatment

During radiation treatment to the pelvic area, inflammation of the large bowel (colon and rectum) and anus occurs.

You might find that you have some of the following symptoms:

  • loose stool or diarrhoea
  • passing blood from the bowel
  • needing to rush to the toilet, or leakage from the bowel
  • feeling that the bowel has not emptied properly
  • passing excess wind
  • difficulty emptying the bowels
  • bowel pain.

Once the radiation treatment has ended, the inflammation usually settles down over a few weeks or months. But there is some permanent scarring of the bowel.

Bladder changes

The cells lining the walls of the bladder can become permanently damaged. This can make them fragile, so they might bleed. The bladder walls might also become scarred and hardened (fibrosed). If this happens, the bladder holds less urine.

You might find that you have some of the following symptoms:

  • need to pass urine often (frequency)
  • burning sensation when you pass urine
  • unable to wait when you need to empty your bladder (urgency)
  • blood in your urine (haematuria)
  • weak flow of urine and your bladder not emptying completely
  • getting up in the night to pass urine.

Less common bladder symptoms after radiation

  • a small amount of urine leakage (incontinence) – especially if you laugh, sneeze, exercise, or cough
  • pain when passing urine
  • passing blood clots
  • difficulty passing urine, because the radiation treatment can make the tube that drains urine from the bladder (urethra) narrower. This is known as a stricture.

Contact your doctor if any of these symptoms occur, because treatment is available to alleviate them.


If you have had surgery and radiation treatment to lymph nodes there is an increased risk of lymphoedema.

Lymphoedema is a long-term swelling of one or more parts of the body due to a drainage system that does not work properly. If this occurs for you, talk to your doctor or nurse about ways to manage this.

Mouth and throat problems

Radiation treatment can give you a sore or dry mouth or throat and your voice may become hoarse, especially if you are receiving treatment to the head and neck region.

Try some of these ideas:

  • suck on ice blocks
  • drink lots of liquids – carry a sipper bottle with you at all times
  • moisten foods with butter
  • dunk dry biscuits in tea
  • blend foods and eat soups and ice creams
  • ask your dentist, doctor or nurse about artificial saliva
  • if you drink alcohol, do so in moderation and avoid spirits
  • do not smoke.

If you are having radiation treatment to your mouth, your teeth will be more likely to decay. Discuss dental care with your doctor and dentist before your treatment starts, so any dental work can be arranged before your radiation treatment begins.

Skin cancer treatment effects

Radiation treatment affects only a small area of skin and will not make you feel unwell. For a few weeks after treatment, the treated skin will be red and inflamed. During this time it will look as though the treatment has made things worse rather than better. Try not to be worried about this.

After a few weeks the area will dry up and form a crust or scab. Over another week or so the scab will peel away, leaving healed new skin underneath. It is important not to pick at the scab. At first, the new skin will look pinker than the skin around it.

Relationships and sexuality

For some people, having cancer and treatment for it has no effect on their sexuality and sex lives. Sometimes the anxiety and/or depression felt by some after diagnosis or treatment can affect their sexual desire.

It is important for you to share your fears and needs with your partner. Sexual intercourse is only one of the ways that you can show affection for one another. Gentle touches, cuddling, and fondling can also reassure you of your need for one another.


Radiation treatment to the pelvic area can cause inflammation of the walls of the vagina. When inflammation reduces, scar tissue can form, which can make the vagina narrower and shorter. The vaginal walls might be dry and thin, and can stick together.

Less vaginal lubricant may be produced, which can make you more likely to get vaginal infections such as thrush. To help keep the vagina supple and to prevent scar tissue from forming, you will be advised to use vaginal dilators (tampon-shaped plastic devices).

Regular sexual intercourse can also help to keep the vagina healthy, although this might initially be uncomfortable. You can also use a vibrator or your fingers to gently stretch the vagina to keep it supple and make sexual intercourse and vaginal examinations more comfortable. Ask your doctor or treatment team for more information.


Men who undergo radiation treatment to the pelvis might also experience loss of interest in sex, temporary impotence, and tiredness. These effects can be distressing, and might last for several weeks after radiation treatment has finished. Sometimes impotence is permanent.

Fertility and contraception

If you are having pelvic radiation and/or some chemotherapy combinations, you might become infertile either temporarily or permanently. Talk to your doctor about this before you start treatment.

Despite the possibility of infertility, contraception should be used (if the woman has not gone through menopause) to avoid pregnancy. There is a risk of miscarriage or birth defects for children conceived during treatment.

If you are pregnant now, talk to your doctors immediately.

Talk to someone you trust if you are experiencing difficulties or ongoing problems with sexual relationships. Friends, family members, radiation therapists, nurses, or your doctor might be able to help. Your local Cancer Society can also provide information about sexual counselling services.

Learn more

Treatment symptoms and side effects Cancer Society of NZ
Radiation treatment handout Cancer Society of NZ, 2018

Credits: Editorial team. Last reviewed: 16 Jan 2015