Why do chemotherapy and radiation treatments cause side effects?
Chemotherapy and radiation therapy fight cancer by destroying cancer cells. Although chemo and radiation are designed to kill cancer cells while sparing healthy tissue, these treatments sometimes damage or destroy normal cells. The harm to normal cells may cause side effects.
The good news is that while damaged cancer cells die, normal cells can repair themselves. Most people receive chemotherapy and radiation spread out over multiple sessions to give normal cells time to repair. Allowing your body adequate recovery time can lessen side effects.
In the meantime, knowing what side effects to expect and how to manage them can empower you to cope with cancer treatments more effectively.
What are common side effects of chemotherapy and radiation?
Your experience of chemotherapy and radiation will depend on your overall health and the specific types of chemotherapy drugs or radiation therapy treatment you’re receiving. Whether you’re receiving a combination of treatments also matters.
You may experience some of the following side effects or none at all. Your oncologist — the cancer specialist in charge of your treatment — is your best resource for explaining what side effects to expect, given your health and treatment plan.
Fatigue is the most common side effect of chemotherapy and radiation. During treatment, your body is not only fighting cancer, but it’s also working to repair cell damage from treatment. As a result, you may feel too drained to carry out your usual activities. Fatigue may set in gradually, allowing you time to adjust. It may start suddenly, requiring you to adapt quickly.
Chemotherapy treatments, in particular, can reduce your red blood cell count and lead to anemia. With anemia, you may experience extreme fatigue alongside other symptoms like shortness of breath and a rapid heartbeat (heart palpitations). Contact your healthcare provider immediately if you notice these symptoms.
Recommendations for managing fatigue
- Know your energy levels. Be alert to your warning signs of fatigue, and keep track of when you feel most tired and why. Keep a diary for one week to note your patterns. Understanding your energy levels can help you plan your days more effectively.
- Plan ahead, organize and prioritize daily activities. Expect to have less energy than you once did for everyday tasks. Given the new limitations, decide which activities you must do and which ones you can delay, delegate or eliminate.
- Balance activity with rest. Taking short, frequent rest breaks is just as important as staying active. Balance light daily exercise, like walking, with relaxing activities, like reading or meditating. A short daily nap (30 minutes or less) is a good idea, but don’t sleep so much that you have trouble falling asleep at night.
- Focus on wellness. Eating a well-balanced, nutritious diet, getting enough exercise and sleep, and managing stress are always important. But they’re essential during cancer treatment and recovery. Speak to a nutritionist for meal planning advice. Talk to a behavioral health specialist, like a psychologist or counselor, for tips on managing stress and getting enough sleep.
Hair follicles are sensitive to radiation and chemotherapy. Although you may experience permanent hair loss, hair usually grows back. It usually starts to regrow within two to three months after chemotherapy and three to six months after radiation therapy. Your hair’s texture and color may be different once it grows back.
Recommendations for managing hair loss
- Plan for changes in your appearance. Plan your new look beforehand if you know it’s likely you’ll experience hair loss. You can have a wig made that matches your hair’s color and style. You can plan outfits that incorporate hats, head wraps or scarves. Ask about the “Look Good Feel Better” program, which the Personal Care Products Council established. This program helps people learn how to manage the appearance-related side effects of cancer treatment.
- Be gentle with your hair. Avoid frequent shampooing or excessively combing or brushing your hair. Avoid using products that can damage your hair, including hair spray, oils, creams or styling tools that use heat (dryers, curling irons, rollers). Use warm water to wash your hair, and gently pat dry with a towel.
- Protect your head and scalp. Protect your head from the sun, cold and wind by wearing a head covering when you’re outside, like a cap, turban, scarf or a hat made of cotton or a cotton blend.
Chemotherapy and radiation therapy can cause skin irritation, itchiness, dryness, redness and swelling. These treatments can also cause your skin to change color or darken. Radiation therapy may cause skin sores that you need to monitor for infection. These sores (and other skin changes) only appear on body parts receiving radiation. Skin rashes, including hand-foot syndrome, are common during chemotherapy. Chemotherapy may also make you sensitive to sunlight, increasing your risk of sunburn.
Most rashes and other forms of skin irritation improve after treatment but require time for healing.
Recommendations for managing skin changes
- Wash with care. Gently cleanse your skin using lukewarm water and mild soap. Pat your skin dry with a soft towel instead of rubbing it.
- Avoid products that may irritate your skin. Don’t apply ointments, creams or powder to the affected area of your skin unless your healthcare provider has prescribed these products. Don’t apply cosmetics, shaving lotions, perfumes or deodorants to the affected area. Use only an electric razor if you need to shave within the affected area.
- Don’t apply direct heat or cold to your skin. Avoid using heating pads, hot water bottles or ice packs on sensitive areas of your skin.
- Allow your skin to breathe. Avoid tight-fitting clothing or clothes made from harsh fabrics that can irritate your skin, like wool or corduroy. Instead, choose clothes made from natural fibers such as cotton. Don’t apply medical tape or bandages to affected skin unless your provider tells you to.
- Shield skin from direct sunlight. Sun exposure might intensify skin reactions and lead to severe sunburn. Wear a large-brimmed hat or protective clothing to minimize sun exposure. Apply sunscreen of SPF 30 or higher to skin you can’t cover.
Nausea, vomiting and diarrhea
Both chemotherapy and radiation therapy can cause diarrhea, nausea and vomiting. The type of medicine you’re taking, how it’s administered, the dose and how frequently you’re taking it all influence whether you’ll experience these symptoms. Unless it’s managed, you may lose too much water (dehydration) or other nutrients you need.
Nausea and vomiting related to chemotherapy is called chemotherapy-induced nausea and vomiting (CINV). Chemotherapy can cause you to become temporarily lactose intolerant. If you notice more diarrhea or loose stools with milk or milk products, you may want to decrease or eliminate these foods or drinks until you have regular stools.
You’re more likely to experience nausea and vomiting with radiation therapy directed toward your brain or abdomen. You’re more likely to experience diarrhea and other forms of gastrointestinal upset (gas, cramps, bloating) with radiation directed at your pelvis.
Recommendations for managing nausea, vomiting and diarrhea
- Get enough fluids. Drink six to eight 8-ounce glasses of fluid per day to prevent dehydration. Choose cold beverages, such as flat soda, pulpless fruit juices or flavored drink mixes. You can also choose ice cubes, popsicles or gelatin. Instead of drinking beverages with your meals, drink between meals.
- Eat mindfully. Avoid eating foods that are hard to digest, such as spicy, fried or high-fat foods. Avoid milk and dairy products if they’re causing diarrhea, as well as foods that can cause gas, such as cabbage, broccoli, corn and peas. Eat small, frequent meals throughout the day instead of three large meals. Nausea is often worse if your stomach is empty. When you do eat, chew slowly. Eating or drinking too fast can promote vomiting.
- Time meals around cancer treatments. Eating immediately before or after cancer treatment can increase your risk of nausea. Allow yourself time between cancer treatments for meals.
- Rest and relax. It’s a good idea to rest after eating to allow food to digest. Some people find relaxation methods or self-hypnosis decreases nausea. Talk with your healthcare provider about relaxation techniques that can keep your stomach feeling settled.
- Take medicine as needed. Tell your healthcare provider if you’re having trouble keeping fluids or foods down. Tell them if you have diarrhea more than two or three times a day or if you notice mucus or blood during a bowel movement. Your provider might prescribe medicines that can help with symptoms and prevent dehydration.
Loss of appetite or difficulty eating
Side effects like nausea, vomiting and diarrhea can make you less inclined to eat. Still, you may lose your appetite or have trouble eating for other reasons.
- Changes in your sense of taste. Some chemotherapy drugs can change your taste buds so bitter foods taste bitterer than usual, sweet foods taste less sweet and food, in general, has a metallic taste. Radiation for head and neck cancers can also change the way food tastes. It can cause dry mouth, making foods taste less flavorful and eating less enjoyable. These changes often get better after treatment.
- Trouble chewing or swallowing. Radiation to your mouth or throat can damage the tissue, making it painful and difficult to swallow (dysphagia). Mouth sores and a sore throat are common chemotherapy side effects. Some people receiving chemotherapy experience heightened sensitivity to hot and cold foods. These symptoms may make eating feel uncomfortable or even painful.
Recommendations for managing appetite loss and eating difficulties
- Improve the taste of food. Rinsing your mouth before you eat can help improve the taste of food. To combat metallic tastes, try sour fruits or fruit-flavored sourballs. Avoid using metal utensils or cookware. If your taste is dulled, you can try increasing the aroma of the foods you eat. Food that smells good also tastes better. You can also experiment with new seasonings, like salad dressings.
- Combat dry mouth. Sipping liquids frequently while eating can keep food moist and help with swallowing. Sucking ice chips or sugar-free candy between meals can help keep your mouth moist. Making meal substitutions, like choosing liquid nutritional drinks, can help with dry mouth. Artificial saliva and Biotene® products can also help.
- Be gentle with mouth sores. You can avoid irritating mouth sores by eating foods that are soft and served warm or at room temperature. Steer clear of foods that irritate your mouth, like carbonated beverages, and crunchy or acidic foods (like citrus). If your mouth sores are too much to handle with your regular diet, your healthcare provider may recommend a soft diet.
Trouble remembering and concentrating
It’s common during cancer treatment to experience trouble thinking, concentrating or remembering. Usually, people experience issues with short-term memory in particular. Regardless of your treatment, the stress of a cancer diagnosis can make it more challenging to think and concentrate. You may be able to carry out your routine, but it may take longer than it once did.
Treatments can impact your brain function, too. Radiation therapy directed at your head can affect your ability to process information. Chemotherapy brain fog, or “chemo brain,” is common among people receiving chemotherapy treatments. In addition to taking more time to think, remember and carry out tasks, you may have trouble sleeping and lose your appetite. Heightened day-to-day stress can lead to depression, which can worsen symptoms.
Recommendations for dealing with thinking difficulties
- Keep your brain rested. Getting at least eight hours of sleep each night is important to keep your brain rested and sharp. During the day, note when you’re thinking most clearly. (First thing in the morning? After a nap? Before bed?). Complete important activities when you’re most alert.
- Keep your mind and body in shape. Getting light daily exercise improves your entire well-being, including your brain function. You can also “exercise” your brain by reading regularly, completing puzzles and participating in other activities that challenge your mind. Ask your healthcare provider to recommend resources and activities.
- Keep notes and stay organized. You can reduce the strain on your memory by taking notes and having a set place where you keep them. Organize household items so you can find them easily.
Radiation toward your pelvis and some chemotherapy drugs can irritate your bladder, making it hard to pee or empty your bladder. You may notice pain or a burning sensation when you pee, or you may feel the constant urge that you need to go to the bathroom.
It’s crucial to watch for signs of a urinary tract infection (UTI), like pelvic pain, cloudy or bloody urine and a fever. UTIs are always unpleasant, but they can be serious when receiving cancer treatment. Report symptoms to your healthcare provider immediately.
Recommendations for managing bladder issues
- Balance your fluid intake. Drink six to eight 8-ounce cups of liquid daily, but avoid beverages like coffee and alcohol that increase how often you have to pee.
- Reduce your risk of infection. Prevent infections by taking showers instead of baths, wearing cotton underwear and avoiding tight-fitting pants. Follow your healthcare provider’s instructions about caring for your catheter if you use one.
- Plan trips to the bathroom. Plan bathroom breaks every few hours and take time to pee before exercise and bedtime.
Sex and fertility issues
The stress of a cancer diagnosis and treatments can take a toll on your sex life. Factors that impact desire — such as fatigue, hormone changes or changes in your self-image — may also play a role in your ability to have children after cancer treatment.
In women and people assigned female at birth (AFAB):
- Chemotherapy can decrease your estrogen levels, causing symptoms like vaginal dryness and conditions like primary ovarian insufficiency. With this condition, ovaries stop producing eggs prematurely (before age 40).
- Radiation directed toward your pelvis can harm your ovaries and interfere with estrogen and egg production. Radiation therapy directed at your head can interfere with the glands that control sex and pregnancy hormones.
In men and people assigned male at birth (AMAB):
- Chemotherapy can decrease your testosterone levels and sperm count. Some chemotherapy medicines can harm the fetus if you impregnate someone during treatment.
- Radiation can also lower your testosterone and sperm count. Radiation directed toward your pelvis can keep you from getting an erection if the X-rays damage the blood vessels or nerves near your penis. Radiation that damages your prostate can prevent you from ejaculating during orgasm.
Recommendations for managing sex and fertility issues
- Speak with your healthcare provider about pregnancy plans before treatment. Prepare for treatment by discussing your concerns about fertility and your desire to have children with your healthcare provider. Some ways to increase your chances of having children after cancer treatment include sperm banking and cryopreservation, assisted reproduction techniques such as in vitro fertilization (IVF), and intra-cytoplasmic sperm injection. If you wish to start a family, talk to your healthcare provider about timing your pregnancy so it’s safe.
- Speak openly with your provider about sex-related issues. Your provider can offer guidance on when it’s safe to have sex. They may be able to recommend medications to help improve your sex life if you’re experiencing symptoms like vaginal discomfort or erectile dysfunction.
How do chemotherapy and radiation affect various organs and body systems?
Side effects often relate to what areas of your body and which body systems treatment will impact most.
Radiation side effects are often site-specific, which means you’re most likely to experience side effects in the parts of your body exposed to X-rays. For example, you’re more likely to notice hair loss or skin changes on the body part receiving the radiation. Fatigue is common regardless of the body parts receiving treatment.
- Hair loss.
- Skin changes.
- Memory loss.
- Trouble concentrating.
Head and neck
- Hair loss.
- Skin changes.
- Mouth and throat sores.
- Trouble speaking or swallowing.
- Taste changes.
- Underactive thyroid.
- Dry mouth.
- Trouble swallowing or breathing.
- Skin changes.
- Nausea and vomiting.
- Decreased appetite.
- Nausea and vomiting.
- Bladder problems.
- Sexual dysfunction and fertility issues.
Chemotherapy targets fast-growing cells in your body. This includes cancer cells, but other cells that tend to grow rapidly can be affected, too. Symptoms often depend on the type of cells affected.
- Skin changes.
- Darkened or discolored skin.
- Tender hands or feet.
Hair follicle cells
- Hair loss.
- Cells in your mouth and digestive tract
- Nausea and vomiting.
- Mouth sores.
Blood-forming cells in your bone marrow (red blood cells, white blood cells and platelets)
- Symptoms of anemia (too few red blood cells).
- Symptoms of neutropenia (too few white blood cells).
- Symptoms of thrombocytopenia (too few platelets).
When do radiation and chemotherapy side effects start?
You may experience side effects within a few hours of treatment — as is the case with certain chemotherapy treatments — that gradually begin to improve. Or you may not experience side effects until you’ve completed several treatment sessions, as is sometimes the case with radiation. Talk to your healthcare provider about when you’re most likely to experience side effects based on your treatment type and schedule.
How long do radiation and chemotherapy side effects last?
Most side effects go away within a few months after you finish treatment. Still, some side effects don’t start until months or years after treatment. In some cases, side effects can be permanent. Ask your oncologist about what to expect. Ask them to connect you to palliative care resources to help manage cancer symptoms and treatment side effects.
A note from Cleveland Clinic
Every person’s cancer treatment experience is unique. Some common side effects might not affect you, or you may have a side effect not listed here. Your healthcare provider can inform you of signs and symptoms you should look for. Still, only you know how you feel. Let your oncologist and palliative care team know what you’re experiencing. They can recommend ways to manage side effects. Your oncologist can adjust your treatments if necessary.