Two of the most miserable side effects are mouth ulcers and changes in taste, and neither gets much airtime.
A sore mouth makes eating, drinking and talking uncomfortable at exactly the point you need to be keeping your strength up. And taste changes are stranger than people expect. Food doesn't just taste worse. It tastes wrong, in a way that's oddly hard to explain to anyone who hasn't had it.
Both usually pass. Here's what helps in the meantime.
Why do mouth ulcers happen during chemo?
The cells lining your mouth divide quickly, which makes them a target for treatment in the same way hair follicles are. When they're damaged, the lining gets inflamed and sore, and ulcers can form on your tongue, cheeks, gums or throat. The medical name is mucositis.
Taste works differently. Treatment affects the taste buds themselves and the nerves that carry the signals, and some drugs come through in your saliva. That's what produces the metallic taste people describe.
Not everyone gets either. It depends heavily on which drugs you're having, and hormone therapies and bone-strengthening drugs don't usually cause a sore mouth at all.
When might I get a mouth ulcer during chemo?
There's a fairly predictable pattern with chemotherapy.
Mouth soreness tends to start around five to ten days after treatment begins, is often at its worst around days ten to fourteen, and settles roughly two weeks after it started. So on a three-week cycle you may get a bad patch in the middle and feel fine again by the time the next round comes.
Once treatment finishes, it usually clears within a few weeks. Taste often takes longer, sometimes a couple of months, and can drift back gradually rather than switching back on.
See a dentist before you start, if you can
This is the tip people wish they'd had. If there's time between diagnosis and starting treatment, get a dental check.
Sorting out anything that needs doing beforehand is far easier than dealing with it mid-treatment, when your immune system is lower and dental work often has to wait. Tell the dentist you're about to start cancer treatment.
Looking after your mouth during chemo
A boring routine makes a real difference here, and it's worth doing before anything hurts rather than after.
- Brush after meals and before bed with a small-headed, soft toothbrush, and plenty of people switch to a baby's toothbrush
- Use an alcohol-free mouthwash, as alcohol-based ones sting and dry the mouth
- Skip whitening and abrasive toothpastes, which irritate an already sore lining
- Keep sipping water through the day, since a dry mouth gets sore faster
- Clean dentures properly and tell your dentist if they start rubbing
- If your team prescribe a mouthwash, use it as directed even if you dislike it. It only works if it's used regularly.
Eating with a sore mouth
Soft, moist and bland is the whole strategy.
Easier: soup, scrambled egg, yoghurt, porridge, mashed potato, pasta with a smooth sauce, milk puddings, ice cream, smoothies, anything with gravy or extra sauce on it.
Harder: crisps, toast, crusty bread and anything sharp enough to scrape. Citrus and other acidic foods. Spicy food. Very salty food. Very hot food, in both senses.
A few practical tricks: Cut things smaller and chew properly, add sauce or gravy to moisten, drinking through a straw helps some people bypass the sore bits, and cool or room-temperature food is usually kinder than hot.
Sucking ice lollies, crushed ice or small pieces of frozen fruit soothes soreness for a lot of people.
Should I suck ice during cancer treatment?
You may have read that sucking crushed ice during a chemotherapy infusion reduces the risk of mouth ulcers. It's a real thing, and it works by narrowing the blood vessels in your mouth so less drug reaches the lining, similar in principle to a cold cap for your scalp.
The important part is that it's only appropriate with certain drugs, and it isn't right for everyone. Ask your team before trying it rather than turning up with a flask of ice.
When food tastes of metal
- Swap metal cutlery for plastic or wooden, which is the single most effective trick for metallic taste
- Rinse your mouth before eating to wake up your taste buds
- Sugar-free mints or boiled sweets shift an unpleasant taste between meals
- Cold and fizzy drinks stimulate taste more than warm ones
- Marinades, herbs and stronger seasoning help some people, though go easy if your mouth is also sore
- If meat has gone metallic, and it commonly does, try chicken, fish, eggs, beans or dairy for protein instead
- Try things you'd never normally eat, since your old favourites tasting wrong is upsetting in a way a neutral food isn't
Fresh or tinned pineapple gets recommended a lot for clearing the palate. It works for many people, but skip it if your mouth is sore, because it's acidic and it will sting.
Life Kitchen's free cookbook is written specifically for people whose taste has been changed by treatment, and it's genuinely good. There's more on it in our post about the Life Kitchen cookbook.
If you can't face eating at all
That happens, especially when a sore mouth and nausea arrive together.
Small amounts often beat proper meals. Liquid calories count, so milkshakes, smoothies and soup all do a job. Ask your team about seeing a dietitian, because most cancer centres have one and referrals are routine.
Do mention it rather than quietly eating nothing. Weight loss and dehydration make everything else harder, including fatigue. And if sickness is the bigger barrier, our guide to managing nausea may be more use.
Ring your team if
- You can't eat or drink because of the pain
- You have a temperature, which with a mouth infection needs the chemo helpline straight away
- You see white patches on your tongue or inside your cheeks, which usually means thrush and needs treating with antifungal medicine
- Your mouth is bleeding
- Ulcers are getting worse rather than better, or aren't clearing
- Your lips or mouth are swelling
Mouth infections matter more during treatment than they would normally, because your immune system is lower. This is not something to see how it goes with.
Painkillers and prescribed mouthwashes are available and they help. Ask rather than putting up with it.
It does go
The mouth heals quickly once treatment finishes, usually within a few weeks. Taste takes longer and often comes back in stages, with one food at a time becoming recognisable again.
People do tell us that a cup of tea tasting like tea again was one of the small moments that made them feel properly better.
Frequently asked questions
When do mouth ulcers start during chemotherapy? Usually five to ten days after treatment begins, often at their worst around days ten to fourteen, then settling roughly two weeks after they started.
What can I eat with a sore mouth during chemo? Soft, moist and bland. Soup, scrambled egg, yoghurt, porridge, mashed potato and milk puddings all work. Avoid crunchy, spicy, salty, acidic and very hot food.
Why does everything taste metallic during chemotherapy? Treatment affects your taste buds and the nerves carrying taste signals, and some drugs come through in your saliva. Plastic or wooden cutlery is the most effective simple fix.
How long do taste changes last after chemo? Usually a few weeks to a couple of months after treatment ends. Taste often returns gradually, with different foods coming back at different times.
What mouthwash should I use during chemotherapy? An alcohol-free one, or a salt water rinse made with a teaspoon of salt in a pint of water, mixed fresh daily. If your team prescribe a mouthwash, use theirs as directed.
When should I call about mouth problems? Ring your chemo helpline if you can't eat or drink, have a temperature, see white patches suggesting thrush, have bleeding, or if ulcers are worsening rather than healing.
Not medical advice. Mouth infections need treating promptly during chemotherapy, so contact your team rather than waiting.
