The side effects of radiation therapy for breast cancer depend on the type of radiation therapy you’re having (external or internal brachytherapy), the technique (whole-breast or partial-breast radiation), and the area being treated (the breast or an area where the cancer has spread, such as the lymph nodes).

In general, radiation side effects tend to develop as treatment goes on and may be more troubling toward or after the end of treatment. Overall, the most common side effects of radiation are fatigue, redness, swelling, and skin peeling in the area being treated.

Radiation side effects may continue to get worse for a week or so after your treatment is completed, but then your skin will start to heal.

One of the main side effects of external radiation therapy is skin changes in the treated area.

The reaction is much like a sunburn, with redness and possible itching, burning, soreness, peeling, blisters, or darkening of the skin. These skin changes happen gradually over the course of treatment and may happen only in certain areas.

Places where skin touches skin, such as the armpit and the area under the breasts, and places where you may have had a lot of sun exposure, such as the upper chest, are more likely to be affected. Some people have a change in skin color that lasts for years after treatment.

Some people may have telangiectasias (sometimes called spider veins) develop months to years after radiation to the breast. A telangiectasia is a small patch of tiny blood vessels on the skin of the treated area that looks like a tangle of thin red lines. Telangiectasias are not a sign of cancer recurrence, but they can sometimes cause bothersome symptoms such as itching or pain. If you develop telangiectasia after radiation therapy and wish to treat it, you can talk to a dermatologist (skin doctor) about laser therapy or other treatments.

You may be more likely to have significant skin side effects if you have fair skin, larger breasts, certain health conditions that affect skin healing (such as a connective tissue disorder), or had mastectomy or chemotherapy before radiation.

Other common side effects of external radiation therapy are:

Other, less common side effects that external radiation may cause are:

arm swelling (lymphedema) , particularly in cases where lymph nodes are treated

The main side effects of brachytherapy are:

skin changes in the treated area, including redness or bruising

damage to fatty tissue in the breast

fluid collecting in the breast

There are a number of things you can do to help make your skin less sensitive during radiation treatment and also help your skin heal after radiation treatment is completed.

Here are some steps you can take to help prevent and treat irritation before and after daily radiation treatments:

Moisturize: At the beginning your radiation treatment, before you have any side effects, moisturize the skin after your daily treatment with a mild ointment. You also can put it on at night — wear an old T-shirt so the ointment doesn't get on your bedclothes. If your skin becomes dry and flakey during the course of your treatment, moisturize frequently and cleanse skin gently.

Wear loose-fitting shirts, preferably made from cotton.

Avoid wearing underwire bras or any bra that digs into your skin. Don’t wear a bra if there are raw areas.

Take care when showering or bathing:

Use warm rather than hot water.

Try to not let the spray from the showerhead directly hit your breast. Let the water hit your shoulder and run down over the affected area.

Avoid strong soaps and soaps with fragrance. Use fragrance-free soaps with moisturizers or soaps made specifically for sensitive skin.

Avoid scrubbing with wash clothes or loofahs.

Avoid skin-on-skin contact: To help prevent redness and skin irritation, avoid skin-on-skin contact that can cause friction, moisture, pressure, and heat. The areas where this most often happens are:

the armpit: where your arm presses against your armpit and the outer portion of your breast

under the breast: along the bottom crease of your breast, where your breast might droop a bit and lie up against your upper belly wall

between the breasts: along your cleavage where the breasts touch each other

Try to keep your arm away from your body whenever possible.

Wear a supportive bra without an underwire to keep your breasts separated and lifted.

If you have large breasts, when you're not wearing a bra, place a soft washcloth or piece of flannel or soft cotton under your breast.

Use cornstarch: Regularly dust the breast area and skin folds with cornstarch to absorb moisture, reduce friction, and keep you smelling fresh. You can use baby powder made from cornstarch (don't use talc) or sifted kitchen cornstarch. Apply it with a clean makeup brush or put some cornstarch into a single knee-high nylon or thin sock and knot it at the top. Gently tap the sock against the skin to dust the surface. If your doctor has recommended using creams or salves, apply those first, then dust the area with the cornstarch.

Treat yeast infections before radiation begins: With or without radiation, yeast infections are common in the skin fold under each breast — particularly during warm weather in women with large breasts. Signs of yeast infections are redness, itchiness, and sometimes a faint white substance on the skin. If you have a yeast infection, take care of it before radiation starts so it gets better, not worse. An anti-fungal cream or powder (such as athlete's foot medicine) usually works well.

Use soothing creams or salves: For mild irritation, itching and burning, you can apply an aloe vera preparation. Or try an over-the-counter hydrocortisone cream. Spread the cream thinly over the affected area 3 times per day but not 1 hour prior to treatment. If areas or your skin become red, itchy, sore, and start to burn, and the over-the-counter hydrocortisone cream stops helping, ask your doctor for an alternative.

Try cool air: Some people get some relief by blowing air on the area with a hair dryer set to "cool" or "air" (no heat).

Don’t rub, scrub, or pick at blisters or peeling skin: If your skin forms a blister or peels in a wet way, leave it alone. The old skin protects the new skin while it grows back underneath. If you develop a blister and it opens, the exposed raw area can be painful and weepy. Tell your doctor if this occurs so you can help keep it from becoming infected. Keep the area relatively dry and wash it with warm water only. Blot the area dry and then apply a non-adherent dressing, such as Xeroform dressings (which have soothing petroleum jelly) or "second skin" dressings made by several companies. To relieve discomfort from blistering or peeling, take an over-the-counter pain reliever, or ask your doctor for a prescription if you need it. If problems become especially troublesome, your doctor or nurse might suggest taking a short break in treatment to allow your skin to recover.

— Last updated on July 27, 2022, 4:29 PM

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