The short answer
Some effects rarely get mentioned up front: food tasting wrong, numb feet, ringing ears, dry eyes, cataracts, and lymphedema that can begin years later. After head or neck radiation, see a dentist every one to two months for six months. Report mouth pain that stops you eating or sleeping.
After head or neck radiation, NCI advises seeing your dentist every one to two months for six months.
Cisplatin, high-dose carboplatin and high-dose brain radiation can cause ringing or hearing loss months or years later.
Report mouth pain that makes eating, drinking or sleeping hard. A fever of 100.4 F (38 C) or higher during treatment is an emergency: call at once, day or night.
Lymphedema can start years after treatment, and pressing the swollen area may leave a dent in the skin.
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The full explanation.
Hair loss and nausea get talked about. Plenty of other effects do not, so when they show up people often assume they are imagining things or that the problem is too small to mention. Below are effects the National Cancer Institute documents, what each is, and whether to report it.
Taste changes
Radiation therapy can change how sweet, sour, bitter, and salty tastes register. Chemotherapy may cause an unpleasant chemical or metallic taste in your mouth. Food can taste bland or simply wrong.
Worth reporting, because taste changes affect how much you eat. Tell your doctor or nurse as soon as you notice changes in your mouth.
Dry mouth
Radiation to the head and neck damages the salivary glands. Dry mouth raises your risk of tooth decay and mouth infections. NCI suggests sipping water often, sugar-free candy, and saliva substitutes that coat, protect, and moisten your mouth and throat. Report it and ask about dental care: after head or neck radiation, NCI advises seeing your dentist every one to two months for six months, and checking with your radiation oncologist before any dental surgery.
Mouth pain and sores
Chemotherapy and immunotherapy can damage the cells lining the mouth, causing pain or swelling. NCI's instruction, on its mouth and throat problems page, is specific: call your doctor or nurse if you have pain in your mouth, lips, or throat that makes it difficult to eat, drink, or sleep. A fever of 100.4 degrees F (38 degrees C) or higher needs a faster response than that. During treatment it is a medical emergency, so call at once, day or night, and go to an emergency department if your team cannot be reached. Other sources put the threshold at 100.4 degrees F (38 degrees C), so use the number your own team gave you.
Nail changes
Nails can crack, cuticles can become swollen or painful, nails can turn yellow, and infections can develop. NCI suggests keeping nails clean and cut short so you do not tear them, and wearing gloves for dishes and housework. Report infections, and ask which nail changes can be managed at home and which need urgent care.
Peripheral neuropathy
Some cancer treatments damage the nerves that carry information between the brain and the rest of the body. This can show up as tingling, numbness, or a pins-and-needles feeling in your feet and hands that may spread, or as losing the ability to sense temperature or pain. Muscle weakness can cause tripping, balance problems, twitching, or cramping. Damage to nerves controlling automatic functions can cause constipation or diarrhea, dizziness or fainting from low blood pressure, sexual problems, or changes in sweating and urination.
NCI's guidance is that if you start to notice any of these problems, talk with your doctor or nurse, and ask which ones to call about. Meanwhile, remove tripping hazards, wear sturdy shoes, check water temperature before use, and check your skin daily for injuries you may not have felt.
Dry eyes and vision changes
Some chemotherapy drugs cause dry eye syndrome, which feels like dryness or like something is in your eye. Chemotherapy, hormone therapy, immunotherapy, and steroid medicines all raise the risk of cataracts, which cause blurred, cloudy, or double vision and sensitivity to light. Report it, and see an ophthalmologist regularly. Dry eye can be treated with prescribed drops or ointments, or by blocking the tear ducts to keep moisture in.
Early menopause and thyroid changes
Cancer drugs and radiation can damage the thyroid, ovaries, and testes. Radiation to the head and neck affects the thyroid; radiation to the pelvis affects reproductive organs. The result can be early menopause, infertility, thyroid problems, or weight gain.
Report it. Thyroid problems are treatable with hormone replacement or other therapy, and there is support available for hot flashes, sexual health, and fertility questions.
Joint stiffness
Radiation therapy, some chemotherapy drugs, and steroids can create scar tissue in and around joints that limits movement. It might show up as trouble opening your mouth wide, or pain when you reach overhead. Tell your doctor early: a physical therapist can give you exercises that reduce pain and improve movement.
Ringing in the ears and hearing loss
Cisplatin, high doses of carboplatin, and high-dose radiation to the brain can cause tinnitus or hearing loss months or years after treatment. NCI says to report ringing or changes in hearing to your doctor right away. An audiologist can test your hearing.
Bone thinning
Chemotherapy, steroids, hormonal therapy, and radiation can thin your bones. You will not feel this happening, which is why regular check-ups matter. Calcium and vitamin D, weight-bearing exercise, avoiding tobacco, and limiting alcohol all help.
Swelling from lymphedema
If lymph nodes were removed or you had radiation to an area with many nodes, fluid can build up between skin and muscle. It feels heavy or tight, and pressing on the swollen area may leave a dent in the skin. It can begin years after treatment. Contact your doctor if you notice these signs, and call right away if you develop a fever or signs of cellulitis such as redness, warmth, and tenderness.
If it is not on this list
New or unusual effects still count. Ask your team which symptoms can be managed at home and which need urgent medical care, and get the after-hours number for your clinic.
When to get help sooner
- Call your care team at once, day or night, if a fever turns up while you are on chemotherapy. The CDC treats fever during chemotherapy as a medical emergency and puts the mark at 100.4°F (38°C) (CDC); NCI uses 100.5°F, so follow whichever number your own team gave you. If nobody picks up quickly, go to an emergency department and tell them you are on chemotherapy.
- Call 911 or go to an emergency department if you cannot breathe properly, or if a red, hot limb comes with shaking chills and confusion.
- Call your care team the same day if a limb with lymphedema turns red, warm and tender, or you develop a fever alongside the swelling. Those are the signs of cellulitis, and it is treated with antibiotics rather than waited out.
- Call your care team the same day if soreness in your mouth, lips or throat is bad enough to stop you eating, drinking or sleeping. If your temperature reaches the threshold your own team gave you, use the emergency route above instead.
- Call your care team within a day or two if ringing in your ears starts or your hearing changes, since NCI says to report those right away, or if numbness, tingling or unsteadiness on your feet is new or spreading.
Sources
- National Cancer Institute: Late Effects of Cancer Treatment. https://www.cancer.gov/about-cancer/coping/survivorship/late-effects
- National Cancer Institute: Mouth and Throat Problems. https://www.cancer.gov/about-cancer/treatment/side-effects/mouth-throat
- National Cancer Institute: Skin and Nail Changes. https://www.cancer.gov/about-cancer/treatment/side-effects/skin-nail-changes
- National Cancer Institute: Nerve Problems (Peripheral Neuropathy). https://www.cancer.gov/about-cancer/treatment/side-effects/nerve-problems
- National Cancer Institute: Lymphedema. https://www.cancer.gov/about-cancer/treatment/side-effects/lymphedema
Words to know
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Common questions
Why does food taste wrong?
Radiation therapy can change how sweet, sour, bitter and salty tastes register, and chemotherapy may cause an unpleasant chemical or metallic taste. Food can taste bland or simply wrong. It is worth reporting because taste changes affect how much you eat, so tell your doctor or nurse as soon as you notice changes in your mouth.
When should I call about mouth pain?
CDC says to call your doctor or nurse if you have pain in your mouth, lips or throat that makes it difficult to eat, drink or sleep. A fever of 100.4 degrees F (38 degrees C) or higher is different: while you are on treatment that is a medical emergency, so ring your team straight away whatever the hour, and head for an emergency department if you cannot reach them. Other sources put the threshold at 100.4 degrees F, so use the number your own team gave you.
What can I do about numb or tingling feet?
Talk with your doctor or nurse as soon as you notice it, and ask which of these problems to call about. In the meantime, remove tripping hazards, wear sturdy shoes, check water temperature before you use it, and check your skin daily for injuries you may not have felt.
Can side effects start years after treatment?
Yes. Tinnitus and hearing loss can appear months or years later, and lymphedema can begin years after treatment too. Bone thinning gives no warning at all, which is why regular check-ups matter. Report ringing or changes in hearing right away, and contact your doctor about new heaviness or swelling.
What if my problem is not on this list?
New or unusual effects still count. Ask your team which symptoms can be managed at home and which need urgent medical care, and make sure you have the after-hours number for your clinic.
Questions to ask your doctor
Being prepared helps you get the most out of your appointments. Save or print these questions.
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Plain-language explanation of the published sources cited on this page. AI-assisted, source-checked, not clinician-reviewed.
Written by: Cancer ExplainedSources last checked: 2026-08-13 what this meansLast updated: 2026-08-20Next planned review: 2027-01-28
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How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and checked line by line against the sources listed on it. That confirms the sources support what the page says. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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