Possible 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. The clinical oncologist can advise you about what to expect.

Skin irritation

Your skin in the treated area may get red, dry and itchy. Dark skin may get darker or have a blue or black tinge. Your nurse or radiographer will give you advice on looking after your skin. If it becomes sore and flaky, your doctor can prescribe creams or dressings to help this.

Skin reactions usually settle down 2–4 weeks after radiotherapy. 

Here are some tips to help with skin irritation:

  • Don’t put anything on your skin in the treated area without checking with your nurse or radiographer first.
  • Have a tepid or warm shower rather than a bath if you can. Turn away from the spray to protect your breast.
  • Pat the area dry gently with a soft towel. Don’t rub the area.
  • Wear loose clothing , as it is less likely to irritate your skin.
  • You need to avoid exposing the treated area to sunshine for at least a year after treatment finishes. Use suncream with a high sun protection factor (SPF) of at least 30 to protect your skin if it’s exposed.

Hair loss

Some men also experience hair loss in the area of their chest that is being treated. This is usually temporary and hair grows back after treatment is over.


Tiredness is a common side effect that may last up to a month or two after treatment. Try to get plenty of rest and pace yourself. Balance this with some physical activity, such as short walks, which will give you more energy.

Aches and swelling

You may have a dull ache or shooting pains in the treated area that last a few seconds or minutes. Sometimes the area becomes swollen. These effects usually improve quickly after treatment.

Long-term side effects

Radiotherapy to the breast may cause side effects that occur months or longer after radiotherapy. These are called late effects. If you’re worried about a particular side effect, 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.