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Mouth soreness, ulcers and dryness can make eating, drinking, speaking and sleeping difficult. Tell your cancer team early, especially if symptoms are changing what you can eat or drink. Gentle mouth care and the right treatment can help, but infection, severe pain and swallowing problems need assessment.
You do not have to wait until ulcers are large or pain is severe. Even a small sore can become a problem when your blood counts are low. Let the team know about discomfort before the next treatment dose, and sooner if it is worsening.
Why does the mouth become sore or dry?
Some cancer treatments make the lining of the mouth inflamed and sore. This is called oral mucositis. Other treatments reduce saliva, the fluid that keeps the mouth moist and helps protect the teeth. Radiotherapy to the head and neck can affect both. Medicines and dehydration can also cause dryness.
These are related but different problems. A sore mouth may need pain relief and assessment for infection; dryness may need saliva support and extra protection against tooth decay. White patches, new bleeding or pain when swallowing should not be treated by simply buying a different mouthwash.
The timing and duration vary with treatment. Soreness may settle between treatment cycles, while dryness after head and neck radiotherapy may last longer. Ask what is expected with your own treatment and what can be done now.
Plan dental care before problems start
Tell your oncology team about broken teeth, dental pain, gum problems or ill-fitting dentures. A dental assessment is particularly important before head and neck radiotherapy and some other treatments. Where possible, needed dental work should be coordinated before treatment begins, allowing appropriate healing time.
Tell your dentist about all cancer treatment, including radiotherapy to the jaws and bone medicines such as bisphosphonates or denosumab. These can change the risks of invasive dental procedures. Do not arrange an extraction without coordination between the dentist and treating team. If there is urgent dental pain or swelling, seek help promptly rather than avoiding care.
Keep a record of the relevant treatment so a new dentist can see it later. Mouth-care precautions may still matter after the main cancer treatment has finished.
A gentle daily mouth-care routine
Brush gently with a soft toothbrush at least twice a day, unless your team gives you a different plan. Use fluoride toothpaste; ask about a mild-flavoured version if your usual paste stings. Clean dentures as advised and leave them out when they rub or your team recommends a break. Keep your lips moisturised with a suitable product.
Do not scrub ulcers or scrape white patches. If brushing causes bleeding or severe pain, ask how to adapt the routine rather than abandoning cleaning for several days. Advice about flossing or cleaning between teeth should reflect your usual practice, gum condition and blood counts.
Your team may recommend a mild salt or bicarbonate rinse and should give you the recipe and frequency. Avoid mouthwashes containing alcohol if they sting. Strong antiseptic mouthwashes are not always helpful.
Chlorhexidine, an antiseptic rinse, is not recommended simply to prevent mouth soreness caused by head and neck radiotherapy, although a dentist may prescribe it for another reason.
Choosing food and drink that hurt less
Soft, moist foods are often easier than dry or rough foods. Examples include soft rice with dal, porridge, well-cooked vegetables with sauce or another familiar meal adapted to your comfort. Let food cool if heat stings. Avoid foods that clearly irritate, such as chilli, sharp acidic flavours or hard crunchy edges.
Try small portions and add moisture rather than forcing a full plate. Ask the team about pain relief before meals if eating hurts. If swallowing is difficult, a dietitian and a swallowing specialist can help identify a safer texture. Do not assume that thinner liquids are always easier or safer.
Report coughing or choking during meals, a wet-sounding voice after swallowing, or food sticking. These symptoms need assessment. If you are losing weight, request nutritional support early; there is no benefit in trying to endure painful eating without help.
What helps a dry mouth?
Frequent small sips can make the mouth more comfortable. Keep water nearby, including at night, while following any medical fluid restriction. A saliva substitute, gel or spray may help. Sugar-free chewing gum or a sugar-free lozenge can stimulate saliva if you can chew and swallow safely and still produce some saliva.
Do not rely on frequent sugary sweets or acidic drinks to moisten the mouth: dryness already makes teeth more vulnerable. A dentist can advise on fluoride protection and how often your teeth need checking. Good daily dental care remains important even when you are eating less.
Some people may be offered a medicine that stimulates saliva, but it is not suitable for everyone and can have side effects. Ask whether it is appropriate for your cause of dryness. No single spray or mouthwash can be assumed to restore damaged salivary glands.
Pain relief and treatment of infection
Tell the team how pain affects drinking, eating and sleep. They may prescribe a mouth treatment or pain medicine. If you use a numbing product, ask about eating and drinking afterwards, because reduced sensation can affect safe swallowing or make it harder to notice hot food.
Fungal, viral or bacterial infections need the right treatment. Do not use leftover antibiotics, someone else's antifungal medicine or a home remedy on an ulcer. Persistent or unusual sores or patches may need review by a dental or oral-medicine specialist.
Avoid tobacco and alcohol, which can irritate the mouth. Check herbal preparations with the team before applying them. A product being labelled natural does not establish that it is safe for damaged tissue or compatible with cancer treatment.
Can mouth sores be prevented?
A regular mouth-care routine can help prevent sores. Your team may recommend cooling inside the mouth for certain chemotherapy treatments and will explain the right method and timing. Do not suck ice during an infusion unless they advise it. Oxaliplatin can cause symptoms triggered by cold, so follow the instructions for your own treatment.
Prevention reduces risk but does not guarantee that sores will not occur. If symptoms develop despite following advice, you have not failed at mouth care. Tell the team so that treatment and nutrition can be adjusted if needed.
When to contact the team urgently
Call your cancer team urgently if pain stops you drinking, you cannot swallow medicines, you pass much less urine, or symptoms worsen quickly. During chemotherapy, a temperature of 38°C (100.4°F) or above needs immediate contact; follow a lower threshold if your unit has given one.
Shivering or suddenly feeling very unwell also needs urgent advice, even without a fever.
Facial swelling, spreading redness, significant bleeding or severe tooth pain also needs urgent advice. Difficulty breathing, rapidly increasing mouth or throat swelling, or inability to swallow saliva needs emergency assessment. Do not wait for your next routine dental appointment.
Common questions
Should I stop brushing when my mouth is sore?
Usually, gentle cleaning remains important. Ask how to adapt the brush, toothpaste and routine if it hurts or bleeds. Avoid vigorous brushing and do not substitute repeated harsh rinses for an individual mouth-care plan.
Is dry mouth just a comfort problem?
No. It can affect eating and speaking and increase tooth decay and infection risk. Ask about saliva support and a dental prevention plan, particularly after head and neck radiotherapy.
What should my caregiver help with?
Keep prescribed mouth-care supplies accessible, help prepare comfortable foods and report reduced intake or new symptoms. Your caregiver should ask which support you want. Encouragement should make care easier, rather than pressure you to eat through pain.
Sources and further reading
- Elad S, et al. MASCC/ISOO clinical practice guidelines for the management of mucositis secondary to cancer therapy. Cancer. 2020;126(19):4423–4431. doi:10.1002/cncr.33100. Read source
- National Cancer Institute. Mouth and Throat Problems: Cancer Treatment Side Effects. Read source
- Mercadante V, et al. Salivary Gland Hypofunction and/or Xerostomia Induced by Nonsurgical Cancer Therapies: ISOO/MASCC/ASCO Guideline. Journal of Clinical Oncology. 2021;39:2825–2843. Read source
- National Cancer Institute. Oral Complications of Cancer Therapies (PDQ). Health Professional Version. Read source
- National Institute of Dental and Craniofacial Research. Cancer Treatments and Oral Health. Read source
- Cancer Research UK. Your mouth and cancer drugs. Patient guidance. Read source
- Hong CHL, et al. Systematic review of basic oral care for the management of oral mucositis in cancer patients and clinical practice guidelines. Supportive Care in Cancer. 2019;27(10):3949–3967. doi:10.1007/s00520-019-04848-4. Read source
- Cancer Research UK. Oxaliplatin. Cold precautions. Read source
- National Cancer Institute. Infection and Neutropenia during Cancer Treatment. Read source
Medically reviewed and approved by Dr (Prof) Vijay Agarwal
Professor and Lead Consultant – Medical Oncology
