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Side Effects of Chemotherapy and Radiation

What Is Cancer?

Cancer happens when cells divide and multiply much faster than most normal cells. Uncontrolled cell growth can lead to masses of cancer cells called tumors, or to a situation where healthy cells are crowded out and can no longer do their jobs well.

What Are Side Effects?

Chemotherapy (or "chemo") and radiation therapy are the two most common types of cancer treatment. They work by destroying these fast-growing cells. But other types of fast-growing healthy cells (such as blood cells and hair cells) also can be damaged along with cancer cells, causing adverse reactions, or side effects.

Side effects can range from tiredness and nausea to hair loss and blood clotting problems. Because each person responds a little differently to treatment and it's hard for doctors to predict exactly how the body will react, they'll closely watch a child who is being treated for cancer. Doctors weigh the amount and severity of side effects against the benefits of treatments.

Fortunately, most side effects are temporary. As the body's normal cells recover, these problems start to go away. There are also good supportive treatments that can lessen the side effects.

Side effects vary:

  • Some can be merely unpleasant, while others can be much more serious.
  • Some show up right away, while others develop over time.
  • Some kids have just a few, while others have many over the course of treatment.

What Are Common Side Effects of Chemo and Radiation?

Chemo and radiation cause similar side effects. Chemo is a general term for a wide variety of medicines used to treat cancer. Chemo's side effects depend on the type of drug used, the dosage, and a child's overall health. These effects are more likely to affect the whole body.

Radiation's side effects tend to affect the area being treated. But they do still depend on the dose of radiation given, the location on the body, and whether the radiation was internal or external.

Here are some of the side effects associated with these cancer treatments, and how to manage them:


Tiredness (fatigue) is the most common side effect of both chemotherapy and radiation. Even the most active kids are likely to find themselves exhausted and perhaps even a little "foggy-headed" during treatment — and possibly for a while afterward. This is normal. Encourage your child to scale back on activities and to rest as much as possible. When treatment is over, your child's energy should return.


Some chemo drugs cause headaches, muscle pains, stomach pains, or even temporary nerve damage that can result in burning, numbness, or tingling in the hands and feet. If this happens, your doctor can prescribe medicines that can help. Never use over-the-counter or herbal medicines without your doctor's OK, though, as these can interact with the chemo drugs.

Mouth, Gum, and Throat Sores

Both chemo and radiation (specifically to the head and neck) can lead to mouth sores, sensitive gums, an irritated throat, and an increased risk of tooth decay. The doctor may prescribe a mouth rinse or pain medicine to help with symptoms. Soft, cool foods might be easier to eat, and your child should avoid high-acid foods and juices (like oranges or tomatoes) during times of soreness. Regular dental checkups are important too, but check with your child’s doctor first to make sure it's a safe time to go to the dentist.

Gastrointestinal Problems

Many types of chemo drugs are known to cause nausea, vomiting, loss of appetite, constipation, or diarrhea. Medicines can prevent or ease a lot of these symptoms. It's also common for kids to find that their taste preferences change while on chemo (they can't tolerate certain smells or textures, for example).

If your child doesn't have much of an appetite, try offering several small servings of something rather than three large meals. Also concentrate on keeping your child hydrated with water, juices, and broths.

Gastrointestinal symptoms related to radiation tend not to be as severe as those from by chemo, except in children who get radiation to the pelvis or abdomen.

Skin Changes

Chemo drugs commonly cause rashes, redness, and other types of skin irritation — especially if your child had radiation before the chemo (this is called "radiation recall"). Radiation alone can cause similar symptoms, along with blisters, peeling, and swelling in the treatment area.

Wearing loose, soft cotton clothing may help with the discomfort. Your doctor might also recommend or prescribe creams or ointments. Because the affected area can be more sensitive to the sun for a while after treatment, your child should always wear sunscreen with an SPF of at least 30 whenever going outdoors.

Weight Changes

Some kids have weight loss or weight gain. It's common for those taking steroids to have an increased appetite and gain weight in unusual places, like the cheeks or back of the neck. Other kids might have decreased appetites or trouble keeping food down (especially if they're feeling nauseated after chemo).

If you're concerned about your child's weight, talk to the doctor about helping your child maintain a healthy weight based on their medical needs. Working with the dietician on the treatment team will help.

Hair Loss

During chemo, hair thinning and hair loss may happen all over the body. Radiation therapy to the head and neck may cause hair loss in that area. But radiation anywhere else will not cause the hair on the head to fall out.

Though some kids take hair loss in stride, others find it upsetting. Tell your child that the hair will grow back — though it might be a slightly different color or texture. In the meantime, many kids choose to wear baseball hats, bandanas, scarves, or wigs.

Before treatment, some kids get shorter haircuts, as it can be easier to watch shorter strands of hair fall rather than long ones.

Kidney and Bladder Problems

Some chemo drugs affect the kidneys and bladder. Frequent blood tests will check kidney function. Staying well hydrated can help. Tell the doctor if your child has blood in the urine or any problems peeing.


Chemotherapy drugs and radiation can destroy all types of healthy blood cells and harm the body's production of new ones. Low levels of red blood cells (the cells that carry oxygen) can lead to anemia, which causes tiredness, paleness, shortness of breath, and a fast heartbeat.

Frequent blood draws throughout treatment will monitor the levels of these cells. Often, children need blood transfusions during chemo.

Blood Clotting Problems

Platelets are cells that help blood to clot. They also can be affected during cancer treatment, especially chemo. Low platelets, or thrombocytopenia, can lead to bleeding. This may cause bruising; small red spots on the skin (called petechiae); bloody or black bowel movements or vomit; or bleeding from the nose, gums, or line site (the area where fluids and medicines are given to people with cancer).

Kids with a low platelet count have to take it easy to reduce the risk of bleeding. That means avoiding rough play and contact sports (like football), and brushing with a soft toothbrush and flossing very gently. In very serious cases of thrombocytopenia, a child might need a transfusion of platelets.


White blood cells (WBCs) also can be low during or after cancer treatment. WBCs called neutrophils help fight infection. Having too few can put a child at increased risk of serious infection, a condition called neutropenia. A fever can be a sign of serious infection, so tell your doctor right away if your child gets one.

Kids with neutropenia need to take special precautions against germs. Like all kids, they should wash their hands well and often, especially before eating, after using the bathroom, and after touching animals. They also need to avoid crowded indoor places or visiting with friends or family members who have contagious illnesses (such as a cold, the flu, or chickenpox).

To prevent food-borne infection, kids with neutropenia shouldn't eat raw seafood, undercooked meat, or eggs.


Because their immune systems are weaker, kids with cancer (especially those with neutropenia) can't fight off bacteria and other germs that enter the body. So a seasonal virus or infection that seems minor can quickly turn into a life-threatening infection.

Signs of infection include fever or chills, coughing or congestion, vomiting or diarrhea, and pain (perhaps in the ears, throat, belly, or head, or pain when going to the bathroom). Or there might be redness, swelling, pain, or oozing on the skin or around the line site.

If your child has any of these symptoms, especially a fever, contact your doctor right away.

How Long Do Side Effects Last?

Most side effects start to go away after cancer treatment ends and the healthy cells have a chance to grow again. How long this takes typically on a child's overall health and the types and amounts of drugs and/or radiation they had.

Sometimes, though, cancer treatment can cause lasting changes to a growing body. These long-term side effects (called late effects) can include damage to the heart, lungs, brain, nerves, kidneys, thyroid gland, or reproductive organs. In some cases, kids and teens who've had some types of chemotherapy have a higher risk for a second type of cancer later in life.

Before treatment, the doctor will talk to you about your child's risk of late effects and what precautions can be taken before treatment, if any. For example, some teens who undergo treatments that have fertility risks can take preventive measures like egg or sperm preservation.

How Can Parents Help?

Cancer treatment has come a long way. But it can be hard for kids and teens to cope with the sometimes painful or uncomfortable side effects. Fortunately, doctors have many ways to make treatments easier to manage.

Your child also might feel the emotional effects of having a serious illness. Answer questions and help explain what's going on in an age-appropriate way. Turn to the care team when needed. A hospital support group, child life specialist, social worker, or psychologist from the team can help your child and your whole family before, during, and after cancer treatment.

You also can find information and support online at:

Reviewed by: Robin E. Miller, MD
Date Reviewed: May 10, 2022

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