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Mouth sores from cancer treatment (oral mucositis)

Also called: Oral mucositis, chemo mouth sores, radiation mouth sores

Painful redness and sores inside the mouth from chemotherapy or radiation to the head and neck. Gentle mouth care and pain relief help, and it heals after treatment.

Starts5 to 10 days after chemo
Heals2 to 4 weeks after treatment
Watch forFever, can't drink

Overview

Sores can make eating, drinking, and talking hard.

Infections like thrush can happen on top.

Symptoms

Common signs:

  • Mouth sores during cancer treatment
  • Getting chemotherapy, radiation, or other cancer treatment

Less common

  • Mouth pain
  • Trouble eating
  • White patches

When to get medical care

Call 911Fever of 100.4°F or higher during chemo, or can't swallow.
Get care todayCan't eat or drink.
See a doctor soonMouth pain getting worse.

Causes

Chemo and radiation.

Does it spread or run in families?

  • Cancer isn't contagious. You can't catch it from someone.
  • Some cases run in families. Ask whether genetic testing makes sense for you.

Who is more likely to get it

  • Head and neck radiation
  • Some chemo

Possible complications

Diagnosis

Your care team checks your mouth.

The exam

Mouth exam.

Tests

Tests, if needed:

  • Swab: For infection.

Treatment

Keep your mouth clean and moist.

Self-care

  • Rinse with a mix of salt and baking soda in water several times a day
  • Use a soft toothbrush
  • Avoid alcohol mouthwash, spicy, acidic, and rough foods
  • Suck ice chips during some chemo if advised
  • Sip water often

Medicines

Medicines that may help:

MedicineHelps withGood to know
Numbing rinses
PainPrescription.
Pain medicine
Severe pain

OwieClear doesn't give doses: follow the label or your healthcare professional. Medicine names here are examples, not a full list.

Prevention

To lower risk:

  • Dental checkup before treatment

Which doctor treats this

  • Start with your primary care provider (family doctor or internist).
  • They may send you to an oncologist (cancer doctor), often with a surgeon and a radiation doctor.

Living with it

  • Keep a simple diary of symptoms, triggers, and medicines to bring to visits.
  • Bring a list of your medicines and questions to each visit.
  • Ask for a survivorship care plan when treatment ends.
  • Gentle activity, like walking, can ease tiredness.
  • Long-term illness can affect mood. Tell your doctor if you feel down or anxious.

Support groups and helplines

Back to school, work, or sports

  • Most people can keep working or going to school.
  • Ask about changes that help, like extra breaks or a flexible schedule. Workers may be covered by the ADA. Students may get a 504 plan.

Pregnancy and breastfeeding

  • If you're pregnant or planning to be, tell your prenatal provider about this condition.
  • Some cancer treatments can harm a baby. Ask about saving eggs before treatment if you want children later.
  • Don't start or stop any medicine on your own. Some are safe in pregnancy and some need to be changed.
  • Ask before taking any pain reliever. The FDA advises avoiding ibuprofen and naproxen after 20 weeks unless your doctor says to.
  • Breastfeeding: Most medicines are fine, but ask. The NIH LactMed database lists what's known about each one.

For caregivers

  • Go to visits when you can and take notes.
  • Keep a list of medicines, allergies, and doctors in one place.
  • Learn the warning signs that need fast care.
  • Take breaks and ask for help. Caregivers need care too.

Outlook

Heals after treatment.

Getting ready for your visit

Bring a list of your symptoms and medicines.

Questions to ask

  • What rinse should I use?

Research studies

Research studies test new ways to find and treat health problems. Some are looking for volunteers. Talk with your doctor before joining one.

Search ClinicalTrials.gov for studies on Mouth sores from cancer treatment (oral mucositis)

Sources

Last updated 2026-11-12.