You had radiation treatment for cancer. The high-powered radiation (such as x-rays or gamma rays), particles, or radioactive seeds used to kill cancer cells can cause side effects.

Approximately 1 to 2 weeks after external beam radiation treatment starts, you might notice changes in your skin within the treatment area. Most of these side effects go away over several weeks after your treatments have stopped. These changes can be made worse by certain chemotherapies, medicines and excessive sun exposure.

These side effects include:

• Your skin in the treatment field may get red like a sunburn.
• Your mouth can develop irritation or white patches.
• Your skin might start to peel or get dark.
• Your skin may itch.

The hair on your head and possibly your eyebrows may begin to fall out about 2 weeks after radiation treatment starts. It may not grow back. Sometimes if your hair does regrow, it may be different in texture or color than before.

When you have radiation treatment planning, sometimes temporary color markings are drawn on your skin with a magic marker for alignment. Ask your provider if these marks can be removed. Sometimes permanent tattoos (that look like little black or blue dots) are used instead. These marks will not come off if you bathe. Always ask your provider before removing any marks.

To care for your hair:

• For the first 2 weeks of treatment, wash your hair once a week with a gentle shampoo, such as a baby shampoo.
• After 2 weeks, use only warm water on your hair and scalp, without shampoo.
• Dry gently with a towel.
• Do not use a hair dryer, curling iron, or hair straightener.

If you wear a wig or toupee:

• Be sure the lining does not bother your scalp.
• Wear it only for a few hours a day during the time you are getting radiation treatments and right after treatment has ended.
• Ask your provider when you can start to wear it more.

If you are having hair loss in certain areas, sometimes a wig or partial wig can be helpful to cover areas of hairless, you can ask your provider for information.

To care for your skin in the treatment area:

• Wash the treatment area gently with lukewarm water and a gentle cleanser. Don't scrub your skin.
• Don't use strong scented soaps.
• Pat dry instead of rubbing dry.
• Don't use lotions, ointments, makeup, perfumed powders, or other perfumed products on this area without asking your provider what is safe. Generally, baby or scent-free products are the safest.
• Keep the area being treated out of direct sunlight. Wear a hat or scarf. Ask your provider if you should use sunscreen.
• Don't scratch or rub your skin.
• Ask your provider for medicine if your scalp gets very dry and flaky, or if it gets red or tanned.
• Tell your provider if you have any breaks or openings in your skin.
• Don't put heating pads or ice bags on the treatment area.

Keep the treatment area in the open air as much as possible. But stay away from very hot or cold temperatures.

Don't swim during treatment without asking your provider.

You need to eat enough protein and calories to keep your weight and strength up. Ask your provider about liquid or protein bar type food supplements that may help you get enough calories.

Avoid sugary snacks and drinks that may cause tooth decay.

You will likely feel tired after a few days. If so:

• Don't try to do too much. You probably will not be able to do everything you are used to.
• Get more sleep at night. Rest during the day when you can.
• Take a few weeks off work, or work less.
• Ask your provider if you need a medical excuse or leave of absence form.

You may be taking a medicine called dexamethasone (Decadron) while you are getting radiation to the brain.

• It may make you hungrier, cause leg swelling or cramps, cause problems sleeping (insomnia), or cause changes in your mood.
• These side effects will go away after you start taking less of the medicine, or when you stop taking it.

Your provider may check your blood counts regularly and order imaging to follow you.

Contact your provider if you have pain that doesn't go away, a fever, severe vomiting or diarrhea, or blistering of the skin.

Radiation - brain - discharge; Cancer - brain radiation; Lymphoma - brain radiation; Leukemia - brain radiation; CNS radiation; Cranial radiation

American Cancer Society website. Radiation therapy side effects. www.cancer.org/cancer/managing-cancer/treatment-types/radiation/effects-on-different-parts-of-body.html. Updated June 9, 2025. Accessed February 19, 2026.

Doroshow JH. Approach to the patient with cancer. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 164.

National Cancer Institute website. Central nervous system tumors treatment (PDQ) health professional version. www.cancer.gov/types/brain/hp/adult-brain-treatment-pdq. Updated March 28, 2025. Accessed February 19, 2026.

National Cancer Institute website. Radiation therapy and you: support for people with cancer. www.cancer.gov/publications/patient-education/radiation-therapy-and-you.pdf. Updated April 2021. Accessed February 19, 2026.

Updated by: David Herold, MD, Radiation Oncologist in Jupiter, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.