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radiotherapyRadiation therapy is a cancer treatment that uses high doses of radiation to kill cancer cells and stop them from spreading. However, patients should be aware of the side-effects of this treatment.

Many people who get radiation therapy have skin changes and some fatigue. Other side effects depend on the part of your body being treated.

Here are the Radiation Therapy Side Effects:

Hair Loss
Mouth Changes
Nausea and Vomiting
Sexual and Fertility Changes
Skin Changes
Throat Changes
Urinary and Bladder Changes


Diarrhea is frequent bowel movements which may be soft, formed, loose, or watery. Diarrhea can occur at any time during radiation therapy.
Radiation therapy to the pelvis, stomach, and abdomen can cause diarrhea. People get diarrhea because radiation harms the healthy cells in the large and small bowels. These areas are very sensitive to the amount of radiation needed to treat cancer.


Fatigue is a common side effect, and there is a good chance that patients will feel some level of fatigue from radiation therapy.

Fatigue from radiation therapy can range from a mild to an extreme feeling of being tired. Many people describe fatigue as feeling weak, weary, worn out, heavy, or slow.

Fatigue can happen for many reasons. These include:

  • Anemia
  • Anxiety
  • Depression
  • Infection
  • Lack of activity
  • Medicines

Fatigue can also come from the effort of going to radiation therapy each day or from stress. Most of the time, you will not know why you feel fatigue.

Fatigue can last from 6 weeks to 12 months after your last radiation therapy session. Some people may always feel fatigue and, even after radiation therapy is over, will not have as much energy as they did before.

Hair Loss

Hair loss (also called alopecia) is when some or all of the patient’s hair falls out.
Radiation therapy can cause hair loss because it damages cells that grow quickly, such as those in your hair roots.

Hair loss from radiation therapy only happens on the part of the body being treated. This is not the same as hair loss from chemotherapy, which happens all over the body. For instance, the patient may lose some or all of the hair on the head when the patient gets radiation to the brain. But if the patient gets radiation to the hip, the patient may lose pubic hair (between the legs) but not the hair on the head.

The patient may start losing hair in the treatment area 2 to 3 weeks after the first radiation therapy session. It takes about a week for all the hair in the treatment area to fall out. The hair may grow back 3 to 6 months after treatment is over. Sometimes, though, the dose of radiation is so high that the hair never grows back.

Once the hair starts to grow back, it may not look or feel the way it did before. The hair may be thinner, or curly instead of straight. Or it may be darker or lighter in color than it was before.

Mouth Changes

Radiation therapy to the head or neck can cause problems such as:

  • Mouth sores (little cuts or ulcers in your mouth)
  • Dry mouth (also called xerostomia) and throat
  • Loss of taste
  • Tooth decay
  • Changes in taste (such as a metallic taste when you eat meat)
  • Infections of your gums, teeth, or tongue
  • Jaw stiffness and bone changes
  • Thick, rope-like saliva

Radiation therapy kills cancer cells and can also damage healthy cells such as those in the glands that make saliva and the soft, moist lining of your mouth.

Some problems, like mouth sores, may go away after treatment ends. Others, such as taste changes, may last for months or even years. Some problems, like dry mouth, may never go away.

It is important for a patient to visit a dentist at least 2 weeks before starting radiation therapy to head or neck.

Nausea and Vomiting

Radiation therapy can cause nausea, vomiting, or both. Nausea is when the patient feels sick and feel like he/she is going to throw up. Vomiting is when you throw up food and fluids. The patient may also have dry heaves, which happen when the body tries to vomit even though the stomach is empty.

Nausea and vomiting can occur after radiation therapy to the stomach, small intestine, colon, or parts of the brain. The risk for nausea and vomiting depends on how much radiation the patient is getting, how much of the patient’s body is in the treatment area, and whether the patient is also having chemotherapy.

Nausea and vomiting may occur 30 minutes to many hours after the radiation therapy session ends. The patient is likely to feel better on days that he/she does not have radiation therapy.

Sexual and Fertility Changes

Radiation therapy sometimes causes sexual changes, which can include hormone changes and loss of interest in or ability to have sex. It can also affect fertility during and after radiation therapy. For a woman, this means that she might not be able to get pregnant and have a baby. For a man, this means that he might not be able to get a woman pregnant. Sexual and fertility changes differ for men and women.

It is important to tell the doctor if the patient is pregnant before starting radiation therapy.

Problems for women include:

  • Pain or discomfort when having sex
  • Vaginal itching, burning, dryness, or atrophy (when the muscles in the vagina become weak and the walls of the vagina become thin)
  • Vaginal stenosis, when the vagina becomes less elastic, narrows, and gets shorter
  • Symptoms of menopause for women not yet in menopause. These include hot flashes, vaginal dryness, and not having your period.
  • Not being able to get pregnant after radiation therapy is over

Problems for men include:

  • Impotence (also called erectile dysfunction or ED), which means not being able to have or keep an erection
  • Not being able to get a woman pregnant after radiation therapy is over due to fewer or less effective sperm

Sexual and fertility changes can happen when people get radiation therapy to the pelvic area. For women, this includes radiation to the vagina, uterus, or ovaries. For men, this includes radiation to the testicles or prostate. Many sexual side effects are caused by scar tissue from radiation therapy. Other problems, such as fatigue, pain, anxiety, or depression, can affect interest in having sex.

After radiation therapy is over, most people want to have sex as much as they did before treatment. Many sexual side effects go away after treatment ends. But patients may have problems with hormone changes and fertility for the rest of their lives.

Skin Changes

Radiation therapy can cause skin changes in your treatment area. Here are some common skin changes:

Redness– The skin in the treatment area may look as if the patient has a mild to severe sunburn or tan. This can occur on any part of the body where the patient is getting radiation.

Pruritus– The skin in the treatment area may itch so much that the patient will always feel like scratching. This causes problems because scratching too much can lead to skin breakdown and infection.

Dry and peeling skin– This is when the skin in the treatment area gets very dry – much drier than normal. In fact, the skin may be so dry that it peels like it does after a sunburn.

Moist reaction– Radiation kills skin cells in the treatment area, causing the patient’s skin to peel off faster than it can grow back. When this happens, the patient can get sores or ulcers. The skin in the treatment area can also become wet, sore, or infected. This is more common where the patient has skin folds, such as the buttocks, behind the ears, under the breasts. It may also occur where the skin is very thin, such as the neck.

Swollen skin– The skin in the treatment area may be swollen and puffy.

Radiation therapy causes skin cells to break down and die. When people get radiation almost every day, their skin cells do not have enough time to grow back between treatments. Skin changes can happen on any part of the body that gets radiation.

Skin changes may start a few weeks after the patient begins radiation therapy. Many of these changes often go away a few weeks after treatment is over. But even after radiation therapy ends, the patient may still have skin changes. The treated skin may always look darker and blotchy. It may feel very dry or thicker than before. And the patient has a tendency to burn quickly and be sensitive to the sun. Also, the patient will always be at risk for skin cancer in the treatment area. It is important to avoid tanning beds and protect the patient from the sun by wearing a hat, long sleeves, long pants, and sunscreen with an SPF of 30 or higher.

Throat Change

Radiation therapy to the neck or chest can cause the lining of the throat to become inflamed and sore. This is called esophagitis. The patient may feel as if he/she has a lump in the throat or burning in the chest or throat. The patient may also have trouble swallowing.

Radiation therapy to the neck or chest can cause throat changes because it not only kills cancer cells, but can also damage the healthy cells that line the throat. The risk for throat changes depends on how much radiation the patient is getting, whether the patient is also having chemotherapy, and whether the patient uses tobacco and alcohol while getting radiation therapy.

The patient may notice throat changes 2 to 3 weeks after starting radiation. He/she will most likely feel better 4 to 6 weeks after radiation therapy has finished.

Urinary and Bladder Changes

Radiation therapy can cause urinary and bladder problems, which can include:

  • Burning or pain when urinating or after emptying the bladder
  • Trouble starting to urinate
  • Trouble emptying the bladder
  • Frequent, urgent need to urinate
  • Cystitis, a swelling (inflammation) in the urinary tract
  • Incontinence, when the patient cannot control the flow of urine from the bladder, especially when coughing or sneezing
  • Frequent need to get up during sleep to urinate
  • Blood in the urine
  • Bladder spasms, which are like painful muscle cramps

Urinary and bladder problems may occur when people get radiation therapy to the prostate or bladder. Radiation therapy can harm the healthy cells of the bladder wall and urinary tract, which can cause inflammation, ulcers, and infection.

Urinary and bladder problems often start 3 to 5 weeks after radiation therapy begins. Most problems go away 2 to 8 weeks after treatment is over.


Source: National Cancer Institute

For more information, please visit the National Cancer Institute at

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