Side effects of radiotherapy

Skin irritation

Your skin in the treatment 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.

Skin reactions 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 treatment 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 or crop tops, as they are 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.


This 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.

We have more information about coping with tiredness.

Aches and swelling

You may have a dull ache or shooting pains in the breast that last a few seconds or minutes and/or your breast may become swollen. These effects usually improve quickly after treatment. Some women still have occasional aches and pains in the breast area after radiotherapy.

Late effects of radiotherapy

Radiotherapy to the breast may cause side effects that occur months or longer after radiotherapy. If you’re worried about a particular side effect, talk to your cancer specialist.

The most common late effect is a change in how the breast looks and feels. Small blood vessels in the skin can be damaged causing red ‘spidery’ marks (telangectasia) to show. Your breast may feel firmer, and shrink slightly in size. Some women have surgery to reduce the size of the other breast, to improve their appearance if this is a problem.

It’s rare for radiotherapy to cause any heart problems or problems with the ribs in the treated area. Lung problems as a result of radiotherapy are also rare.

We have more information about managing the late effects of breast cancer treatment.

Back to Radiotherapy explained

Radiotherapy for breast cancer

Radiotherapy uses high-energy rays to destroy cancer cells. It may be given after surgery to prevent breast cancer coming back.