Signs & signals

Frequent mouth ulcers: is a lack of nutrients to blame?

By VISTRA Editorial Team · 6 min read

Published 3 Nov 2026 · Updated 3 Nov 2026

Usually not on its own. Common triggers include stress, tiredness, biting your cheek or other mouth injuries, hormonal changes and certain foods. In some, low levels of iron, folic acid or vitamin B12 play a part. You cannot tell from your diet alone, so if ulcers keep coming back, see a doctor.

Mouth ulcers that keep coming back usually have several possible triggers, such as stress, tiredness, biting your cheek or other injuries inside the mouth, hormonal changes and certain foods. In some people, low levels of iron, folic acid or vitamin B12 also play a part. You cannot tell whether you are getting enough from your diet alone, so if ulcers keep coming back, see a doctor or dentist.

Are frequent mouth ulcers linked to a lack of nutrients?

In some people they can be, but it is only one possible factor, and the exact cause is often not known.

What "ร้อนใน" means in this article

In Thai, ร้อนใน is the everyday word for the small, painful sores that form inside the mouth. Some people connect the word with the idea of "heat" inside the body. This article does not go into that idea. Here, it simply means mouth ulcers: small round or oval sores with a yellow centre and a red border, as Ramathibodi Hospital, Mahidol University describes them.

Nutrition is one factor among many

The US National Institute of Dental and Craniofacial Research (NIDCR) says these sores do not have a known cause. Among the possible triggers it lists, alongside injuries, hormonal imbalances and stress, are low levels of folic acid, iron or vitamin B12. MedlinePlus, from the US National Library of Medicine, likewise lists stress, food allergies, a lack of vitamins and minerals, hormonal changes and menstrual periods, and notes that in some cases the cause is unknown. If your ulcers keep coming back, the next step is to talk to a doctor or dentist.

What else makes mouth ulcers keep coming back?

The NHS divides the triggers into things you can try to avoid and things you cannot always control.

Things you can try to avoid	Things you cannot always control
Biting the inside of your cheek	Hormonal changes, such as during pregnancy
Badly fitting dentures or braces, rough fillings or a sharp tooth	Your genes: some families get mouth ulcers more often
Cuts or burns from hard food or hot drinks	Low levels of some vitamins and minerals
A food intolerance or allergy	Some medicines
Damaging your gums with a toothbrush, or an irritating toothpaste	Stopping smoking
Feeling tired, stressed or anxious

Stress, tiredness and hormones

NIDCR lists emotional stress and hormonal imbalances among possible triggers, along with an accidental cheek or lip bite and stopping smoking. Ramathibodi Hospital mentions hormonal changes around menstrual periods and emotional stress. The NHS includes feeling tired among the things you can try to avoid.

Foods and toothpaste

Ramathibodi Hospital gives chocolate, strawberries, nuts and cheese as examples of foods that can set off ulcers in people who react to them. NIDCR advises avoiding hot, acidic or spicy foods, which can cause pain in existing ulcers and may trigger new ones. The NHS advises not using toothpaste that contains sodium lauryl sulphate.

Family history

The NHS lists your genes among the triggers you cannot always control, noting that some families get mouth ulcers more often.

How can I find out if I am getting enough nutrients?

You cannot tell from your meals or from the ulcers alone. If ulcers keep coming back, the reliable way is to see a doctor or dentist.

What a dental check-up covers

The NHS says that at each dental check-up your dentist should examine your teeth, gums and mouth, ask about your general health and any problems since your last visit, and ask about and give advice on your diet, smoking, alcohol use and teeth-cleaning habits. A dental check-up looks at your teeth, gums and mouth; it does not measure how much of each nutrient you are getting.

Getting ready for the appointment

It helps to note how often ulcers appear, how long each one lasts and anything you noticed beforehand, such as a stressful week or a particular food. If you want to know whether your nutrient levels are low, ask the doctor or dentist whether any tests are worthwhile, rather than judging from your diet.

What can I do while I have a mouth ulcer?

Most mouth ulcers clear up on their own. The NHS says they should clear up within a week or 2, and that they need time to heal. NIDCR gives 1 to 2 weeks.

Brushing and mouth care

Use a soft-bristled toothbrush (NHS).
Avoid toothpaste containing sodium lauryl sulphate (NHS).
Keep up regular dental check-ups (NHS).

Food and drink

The NHS suggests:

eating softer foods and drinking cool drinks through a straw
not eating very spicy, salty or acidic food
not eating rough, crunchy food, such as toast or crisps
not drinking very hot or acidic drinks, such as fruit juice

For soft foods and what to skip with a sore throat, see Sore throat: what should I eat, and what should I skip?

Ask a pharmacist

A pharmacist can suggest suitable options for a painful ulcer. Mention any medicines you take, because the NHS lists some medicines among the things that can trigger mouth ulcers.

What everyday mouth care do health agencies suggest?

The habits health agencies suggest are the same as good everyday mouth care.

Brush your teeth twice a day for about 2 minutes, with medium or soft bristles, which the NHS says are best for most people.
Get regular dental check-ups (NHS), and have badly fitting dentures, braces or a sharp tooth looked at, as the NHS lists these among the triggers.
Take note of foods that seem to set off your ulcers (Ramathibodi Hospital, NHS).
Eat a healthy, balanced diet (NHS).

When should I see a doctor or dentist?

See a doctor or dentist rather than waiting if any of these apply.

Sign	Source
An ulcer lasts longer than 3 weeks	NHS
Ulcers keep coming back	NIDCR
The ulcer is different from ones you have had before, for example bigger than usual or near the back of your throat	NHS
It bleeds, or becomes more painful and red	NHS
Ulcers make eating or drinking difficult	NIDCR
The ulcer is large and slow to heal	Ramathibodi Hospital

The NHS also advises seeing a GP if you have ulcers anywhere else on your body. It adds that it is best to get a long-lasting ulcer checked.

Frequently asked questions

I keep getting mouth ulcers. Is it linked to a lack of nutrients?

It can be in some people, but it is only one of many possible triggers. The US National Institute of Dental and Craniofacial Research (NIDCR) says these sores do not have a known cause, and lists low folic acid, iron or vitamin B12 among possible triggers, alongside an accidental cheek or lip bite, hormonal imbalances, emotional stress and stopping smoking. If ulcers keep coming back, see a doctor or dentist rather than guessing.

What else can cause mouth ulcers to come back?

The NHS lists biting the inside of your cheek, badly fitting dentures or braces, a sharp tooth, cuts or burns from hard food or hot drinks, a food intolerance or allergy, an irritating toothpaste and feeling tired, stressed or anxious. Things you cannot always control include hormonal changes, your genes, some medicines and stopping smoking.

Do I need any tests if I get mouth ulcers often?

That is for a doctor or dentist to decide after looking at your mouth and hearing how often the ulcers come back. NIDCR advises seeing a doctor if mouth ulcers recur frequently or make eating or drinking difficult. If you want to know whether your nutrient levels are low, ask whether any tests are worthwhile, rather than judging from your diet.

What should I eat or avoid while I have a mouth ulcer?

The NHS suggests eating softer foods, drinking cool drinks through a straw and eating a healthy, balanced diet. It advises not eating very spicy, salty or acidic food, rough or crunchy food such as toast or crisps, and not drinking very hot or acidic drinks such as fruit juice.

When should I see a doctor or dentist about mouth ulcers?

The NHS advises seeing a dentist or GP if an ulcer lasts longer than 3 weeks, is different from ulcers you have had before, or bleeds or becomes more painful and red. NIDCR advises seeing a doctor if ulcers keep coming back or make eating or drinking difficult.

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