What Is It?
A mouth ulcer is a small sore or break in the lining inside the mouth. It may appear on the inner lips, cheeks, tongue, gums, soft palate, or floor of the mouth.
Most common mouth ulcers are not dangerous and are not contagious. They often look like round or oval sores with a white, yellow, or grey centre and a red border. They can be painful, especially when eating, drinking, brushing teeth, or speaking.
Common recurring mouth ulcers are often called aphthous ulcers. They usually develop over a few days and often heal within 7 to 14 days. They are usually considered mild when there are one or a few small ulcers, no fever, no spreading swelling, and the person can still eat and drink.
Not every mouth sore is a simple ulcer. Blisters, white patches, gum infections, lip sores, oral thrush, hand, foot and mouth disease, dental trauma, allergic reactions, medicine-related ulcers, and rarely oral cancer can look similar. A painless ulcer that does not heal can still be important and should be checked.
Why Mouth Ulcers Are So Common
Mouth ulcers are common because the mouth lining is sensitive and easily irritated. Minor injuries from biting the cheek, sharp food, braces, dentures, broken fillings, hard brushing, spicy foods, stress, hormonal changes, or illness can trigger ulcers in some people.
People often search for mouth ulcers because they can feel more painful than they look. Even a small ulcer can make eating, drinking, talking, or brushing uncomfortable.
What Causes It?
Mouth ulcers can happen for many reasons, and sometimes no clear cause is found.
Common Causes and Triggers
Minor injury or irritation
Accidentally biting the cheek, sharp teeth, braces, dentures, broken fillings, dental work, or hard brushing can damage the mouth lining. Sharp teeth, braces, dentures, or broken fillings can repeatedly rub the mouth lining and delay healing.
Food and oral products
Spicy, acidic, salty, or rough foods may irritate ulcers. Some people are sensitive to certain toothpaste or mouthwash ingredients.
Stress, tiredness, or illness
Stress, poor sleep, viral illness, or general tiredness may trigger ulcers or make them recur.
Nutritional or health factors
Low iron, folate, vitamin B12, or other health conditions may contribute to recurrent ulcers.
Medicines or immune-related conditions
Some medicines and inflammatory conditions can cause or worsen mouth ulcers, especially if ulcers are frequent, large, or slow to heal.
Mouth ulcers are different from cold sores. Mouth ulcers usually occur inside the mouth and are not contagious, while cold sores usually appear on or around the lips and are caused by a virus.
What Should You Do?
If the ulcer is small and mild, first observe its size, number, location, and how long it has been present. Avoid spicy, acidic, salty, or rough foods that make pain worse.
What to Observe First
Pay attention to:
- How long the ulcer has been present
- Whether there is one ulcer or many
- Whether the ulcer is small, large, deep, or spreading
- Whether eating, drinking, or swallowing is affected
- Whether there is fever, swollen glands, rash, or feeling unwell
- Whether there is dental trauma, braces, dentures, sharp teeth, or broken fillings
- Whether ulcers keep returning
- Whether there is unexplained weight loss, bleeding, numbness, or a lump
How to Tell If It Is Mild, Moderate, or Concerning
Mild mouth ulcers are usually small, limited in number, and heal within 7 to 14 days.
Moderate mouth ulcers may be more painful, recurrent, or interfere with eating, drinking, brushing, or speaking.
Concerning ulcers include ulcers lasting more than 3 weeks, large or unusual ulcers, repeated ulcers with illness symptoms, bleeding, weight loss, numbness, or a lump in the mouth or neck.
How Is It Usually Managed?
Mouth ulcers are usually managed by reducing irritation, maintaining gentle oral hygiene, and monitoring healing. General steps may include avoiding trigger foods, using a soft toothbrush, keeping hydrated, and checking for dental causes such as sharp edges or poorly fitting dentures.
A pharmacist can help assess whether the sore sounds like a simple mouth ulcer or whether it may need dental or medical review. This is especially useful if the ulcer is painful, recurring, or affecting eating and drinking.
Seek advice earlier if pain prevents drinking enough fluids, as dehydration can become a concern.
Ask a Pharmacist If Unsure
Ask a pharmacist if the ulcer is painful but small, if it keeps returning, or if you are unsure whether it is a mouth ulcer, cold sore, thrush, injury, or infection.
Seek medical or dental advice earlier for children under 6 years old if ulcers affect drinking, eating, or are linked with fever or rash. Adults aged 65 years and above, people with weakened immunity, cancer treatment, diabetes, recurrent ulcers, poorly fitting dentures, or unexplained symptoms should also seek advice earlier.
When to See a Doctor
See a doctor or dentist if a mouth ulcer is linked with:
- Ulcer lasting more than 3 weeks
- Large, deep, or worsening ulcer
- Recurrent ulcers that keep coming back
- Difficulty eating, drinking, or swallowing
- Fever, swollen glands, rash, or feeling unwell
- Bleeding, numbness, or a lump in the mouth or neck
- Unexplained weight loss
- Ulcers after starting a new medicine
- Symptoms in a child under 6 years old affecting drinking, eating, or linked with fever or rash
- Weakened immunity, cancer treatment, or long-term illness
Quick Summary
- A mouth ulcer is a sore or break in the lining inside the mouth.
- Common recurring mouth ulcers are often called aphthous ulcers.
- Most mild mouth ulcers are not dangerous and heal within 7 to 14 days.
- Not every mouth sore is a simple ulcer; blisters, white patches, cold sores, thrush, and dental problems can look similar.
- Seek advice if an ulcer lasts more than 3 weeks, keeps returning, worsens, bleeds, is painless and non-healing, or affects eating and drinking.
FAQ
What is a mouth ulcer?
A mouth ulcer is a small sore or break in the lining inside the mouth, often causing pain when eating, drinking, speaking, or brushing.
Are mouth ulcers serious?
Most small mouth ulcers are not serious. Ulcers that last more than 3 weeks, worsen, bleed, feel numb, or come with weight loss or lumps should be assessed.
Are mouth ulcers contagious?
Common mouth ulcers are usually not contagious. Cold sores are different and can spread because they are caused by a virus.
How long do mouth ulcers last?
Most mild mouth ulcers heal within 7 to 14 days. Ulcers lasting more than 3 weeks should be checked.
Can stress cause mouth ulcers?
Stress may trigger ulcers in some people or make them recur, but it is not the only possible cause.
Can mouth ulcers be caused by vitamin deficiency?
Recurrent ulcers may be linked with low iron, folate, vitamin B12, or other health factors, but symptoms alone cannot confirm a deficiency.
Is a mouth ulcer the same as a cold sore?
No. Mouth ulcers usually occur inside the mouth and are not contagious. Cold sores usually occur on or around the lips and are viral.
When should I see a doctor for a mouth ulcer?
See a doctor or dentist if the ulcer lasts more than 3 weeks, keeps returning, is large or worsening, causes swallowing difficulty, bleeds, feels numb, is painless and does not heal, or comes with fever, swollen glands, weight loss, or a lump.