What are mouth ulcers?
Mouth ulcers are small sores that develop on the soft tissues inside the mouth — the inside of the lips and cheeks, the tongue, the gums or the floor of the mouth. They are usually round or oval, with a white, yellow or grey centre and a red, inflamed border, and although small, they can be surprisingly painful, particularly when eating, drinking or talking. They are one of the most common minor problems affecting the mouth.
The great majority of mouth ulcers are harmless and clear up on their own within a week or two without any treatment. Many people get them from time to time, and some are prone to recurrent ulcers that come back regularly. While a single ulcer is almost always nothing to worry about, an ulcer that does not heal within about three weeks is the one situation that should always be checked by a doctor or dentist.
Symptoms and what they feel like
Mouth ulcers are usually easy to recognise, and their main feature is localised pain out of proportion to their small size. Typical features include:
- •One or more small, round or oval sores inside the mouth
- •A white, yellow or grey centre with a red, inflamed edge
- •Pain or soreness, especially when eating, drinking or brushing teeth
- •Discomfort made worse by spicy, salty or acidic foods
- •Sometimes a tingling or burning sensation before the ulcer appears
- •Usually no fever or feeling unwell with ordinary ulcers
What causes mouth ulcers?
Many mouth ulcers are triggered by minor damage to the inside of the mouth — for example biting the inside of the cheek, a sharp tooth or filling, hard brushing, or irritation from braces or dentures. Others appear without any obvious injury. Common triggers and contributing factors include stress and tiredness, hormonal changes, and certain foods, and some people find particular things like acidic fruits or a specific toothpaste ingredient set them off.
Recurrent mouth ulcers — where a person gets them repeatedly — can sometimes be linked to underlying factors such as nutritional deficiencies (for example iron, vitamin B12 or folate), or, less commonly, to certain medical conditions affecting the gut or immune system. This is why frequent or severe recurrent ulcers are worth mentioning to a doctor, who can check for any treatable underlying cause. For most people, though, occasional ulcers are simply a common nuisance without a specific cause.
How to relieve and heal mouth ulcers
Because most mouth ulcers heal on their own, treatment is aimed at easing the pain and protecting the ulcer while it recovers. Simple measures help: avoiding foods that make it worse, such as spicy, salty, acidic or very hard foods, and using a soft toothbrush. Rinsing with warm salt water or an antiseptic mouthwash can soothe the area and keep it clean. A pharmacist can recommend treatments such as protective pastes, antiseptic gels, or pain-relieving gels applied directly to the ulcer.
These measures do not necessarily speed up healing dramatically, but they make the days while the ulcer heals much more comfortable. Drinking through a straw can help avoid painful areas, and sticking to softer, blander foods reduces irritation. If ulcers are recurrent, identifying and avoiding personal triggers — a sharp tooth, a particular food, or a toothpaste ingredient — can reduce how often they occur. Managing stress and tiredness may also help those prone to stress-related ulcers.
Preventing recurrent mouth ulcers
For people who get mouth ulcers repeatedly, a few strategies can reduce how often they appear, mostly centred on avoiding known triggers and keeping the mouth healthy. Using a soft toothbrush and brushing gently avoids injuring the lining, and getting a dentist to smooth any sharp tooth or fix an ill-fitting denture removes a common source of repeated ulcers. Avoiding foods that reliably trigger your ulcers, and switching toothpaste if a particular one seems to be a factor, can help.
Because recurrent ulcers are sometimes linked to low levels of iron, vitamin B12 or folate, a doctor may check for these if ulcers are frequent, as correcting a deficiency can reduce them. Managing stress and ensuring good general health also help some people. While these measures can lessen the frequency, some people remain prone to occasional ulcers, and the reassurance that they are almost always harmless and self-healing is itself valuable.
When to see a doctor or dentist
The single most important rule with mouth ulcers is that any ulcer or sore in the mouth that has not healed within three weeks should be checked by a doctor or dentist, even if it is not particularly painful. The great majority of long-lasting ulcers turn out to be harmless, but this three-week rule matters because a persistent sore is the one sign that should never be ignored, and getting it checked provides either treatment or reassurance.
You should also seek advice if you have mouth ulcers that are unusually large, very painful, keep coming back frequently, or are accompanied by feeling generally unwell, a fever, or ulcers elsewhere on the body, as these may point to an underlying cause that benefits from treatment. For recurrent ulcers, a doctor can check for contributing factors like nutritional deficiencies. For the ordinary single ulcer that heals within a week or two, though, no medical attention is needed.