Why Do I Keep Getting Mouth Ulcers? Common Triggers and When to Get Them Checked

Keep getting mouth ulcers? Learn about common triggers, simple ways to ease discomfort, and when a persistent or recurring ulcer should be checked.

26 de agosto de 2026 · 6 min ·por Welleness Guide

Mouth ulcers can be surprisingly disruptive. A small sore inside your cheek or on your tongue may make eating, drinking, or even talking uncomfortable.

For many people, an occasional mouth ulcer is a common problem that clears up on its own. But if they keep coming back, it is natural to wonder why.

There is not always one clear answer. Mouth ulcers can be linked to irritation or injury inside the mouth, while stress, certain foods, nutritional deficiencies, and other factors may also play a role. In some cases, recurring ulcers deserve a closer look from a dentist or doctor.

Here is what to know about common mouth ulcer triggers, what may help with the discomfort, and when it is worth getting checked.

What is a mouth ulcer?

A mouth ulcer is a sore that develops inside the mouth. It may appear on the inside of the cheeks or lips, on the tongue, or elsewhere in the mouth.

They are usually painful and may look round or oval, with a pale or yellowish center and a red edge.

Mouth ulcers are different from cold sores. Cold sores usually develop on or around the lips and are caused by a virus, while ordinary mouth ulcers are not contagious. National Health Service, Mouth ulcers

Most uncomplicated mouth ulcers heal on their own within a week or two. Cambridge University Hospitals NHS Foundation Trust, Recurrent oral ulceration

Common reasons mouth ulcers can develop

An injury or irritation inside the mouth

Sometimes the cause is straightforward.

Accidentally biting the inside of your cheek, brushing too aggressively, eating sharp or hard foods, or burning your mouth with very hot food or drinks can irritate the lining of the mouth.

A sharp tooth, rough filling, braces, or poorly fitting dentures can also repeatedly rub against the same area and contribute to ulcers. University College London Hospitals NHS Foundation Trust, Aphthous ulcers

If an ulcer keeps returning in exactly the same place, it may be worth asking a dentist whether something in your mouth is causing repeated irritation.

Stress and tiredness may play a role

Many people notice mouth ulcers during stressful or particularly tiring periods.

Stress is listed as a possible trigger, although it is not possible to assume that stress is the cause of every ulcer. Mouth ulcers can have several contributing factors, and sometimes no obvious trigger is found. Ashford and St Peter's Hospitals NHS Foundation Trust, Recurrent Aphthous Stomatitis

If you regularly get ulcers, keeping a simple note of when they appear may help you identify patterns involving stress, sleep, diet, or irritation.

Certain foods and drinks can make them worse

Once an ulcer has developed, spicy, salty, acidic, or rough foods can irritate the area and make it more painful.

Foods and drinks that commonly cause discomfort include citrus fruits, fruit juice, spicy foods, crisps, and crunchy toast. This does not necessarily mean these foods caused the ulcer. They may simply irritate an existing sore.

Temporarily choosing softer foods and avoiding anything that noticeably irritates the area may make eating more comfortable while the ulcer heals.

Toothpaste ingredients may matter for some people

Some people find that certain toothpaste ingredients irritate their mouth. The NHS specifically suggests avoiding toothpaste containing sodium lauryl sulphate if it seems to irritate mouth ulcers.

That does not mean everyone with mouth ulcers needs to change toothpaste. But if you notice that ulcers repeatedly appear or become more uncomfortable after using a particular product, discussing alternatives with a dentist or pharmacist may be reasonable.

Could a nutritional deficiency be involved?

In some cases, recurring mouth ulcers can be associated with deficiencies in nutrients such as iron, zinc, folate, or certain vitamins.

However, this does not mean that every recurring ulcer is caused by a deficiency or that taking supplements will solve the problem.

If ulcers are frequent or persistent, a healthcare professional may decide whether further evaluation, including blood tests, is appropriate based on your symptoms and overall health.

Other possible triggers

Hormonal changes and some medicines have also been associated with mouth ulcers. In some people, ulcers may occur more often because of family tendencies.

There are also medical conditions that can be associated with recurrent mouth ulcers. This is one reason frequent or unusual ulcers should not always be treated as something to ignore.

At the same time, it is important not to jump to conclusions. Most mouth ulcers are not a sign of a serious illness. A recurring ulcer does not automatically mean that an underlying medical condition is present.

What can you do to feel more comfortable?

There is no instant fix for every mouth ulcer, but simple steps can reduce irritation while the sore heals.

You may find it helpful to:

Use a soft-bristled toothbrush
Choose softer foods for a few days
Avoid spicy, salty, or acidic foods if they cause discomfort
Avoid rough or crunchy foods that scrape the ulcer
Avoid very hot drinks
Keep up your usual oral hygiene as comfortably as possible

The NHS also notes that a pharmacist may recommend products such as pain-relieving gels or sprays, antimicrobial mouthwash, or other treatments depending on the situation.

If you are considering a medicated treatment, a pharmacist, dentist, or doctor can help you choose an appropriate option.

Can you prevent mouth ulcers from coming back?

Prevention depends on the trigger, and sometimes there may not be a clear one.

If your ulcers appear after a particular type of irritation, addressing that source may help. For example, a sharp tooth or poorly fitting dental appliance may need professional attention.

It can also help to notice possible patterns. You might ask yourself:

Do the ulcers appear after you bite your cheek?
Do they occur during periods of stress or poor sleep?
Does a particular food or toothpaste seem to irritate your mouth?
Are they repeatedly appearing in the same spot?
Have they become more frequent than usual?

A pattern does not prove the cause, but it can give you useful information to discuss with a healthcare professional.

When should you see a dentist or doctor?

Most mouth ulcers are harmless and heal without treatment. However, some situations deserve professional advice.

According to the NHS, you should have a mouth ulcer checked if it lasts longer than three weeks. You should also seek advice if an ulcer is unusually large, different from ulcers you have had before, becomes increasingly painful or red, or is accompanied by other symptoms that concern you.

Frequent recurring ulcers may also be worth discussing with a healthcare professional, especially if they are severe or affecting your ability to eat and drink comfortably.

The important point is not to self-diagnose based on one symptom. A dentist or doctor can assess the ulcer in the context of your overall health and decide whether any further investigation is needed.

The bottom line

Mouth ulcers are common, and an occasional ulcer will often heal on its own within a week or two.

When they keep coming back, possible contributors can include irritation or injury, stress, certain foods, toothpaste ingredients, nutritional deficiencies, medicines, and other factors. Sometimes there is no obvious trigger.

The most useful approach is to pay attention to patterns, avoid things that make an ulcer more uncomfortable, and seek professional advice when ulcers are persistent, unusually severe, or repeatedly returning.