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Mouth sores and ulcers (canker sores)
6-minute read
Key facts
- Mouth ulcers are a type of sore that occurs on the inside of your mouth.
- The exact cause of mouth ulcers is not known, but some factors such as stress, hormonal changes and mouth injuries may make them more likely.
- Most mouth ulcers heal without treatment after 1 to 2 weeks.
- Numbing gel and saltwater mouth rinses can help relieve the symptoms of a mouth ulcer and reduce your chance of infection.
- See your doctor if your mouth ulcer is very painful or if it keeps coming back.
What are mouth ulcers?
Mouth ulcers are a type of sore that forms on the inside of your mouth. They are also known as aphthous ulcers or canker sores.
About 1 in 5 people have recurrent (repeated) mouth ulcers.
What are the symptoms of mouth ulcers?
Mouth ulcers can be very sore or uncomfortable. Eating, drinking, talking, or brushing your teeth may make the pain worse.
What do mouth ulcers look like?
Mouth ulcers are shallow sores with a white or grey top. They are often red around the outside. Most mouth ulcers are smaller than 5 millimetres (mm) across and can occur as a single ulcer or in groups. Some people get ulcers that are larger than 5 millimetres (mm) wide.
Mouth ulcers can appear in different places around your mouth. Common places include:
- inside your lips
- inside your cheeks
- on the bottom of your mouth
- on your gums
- on your tongue
What causes mouth ulcers?
The exact cause of mouth ulcers is not known. There are several factors that can make you more likely to develop a mouth ulcer, including:
- stress, anxiety or hormonal changes
- injury or damage to your mouth, such as from dentures or braces
- reaction to certain foods, such as chocolate, peanuts or coffee
- some diseases, such as coeliac disease
- some medicines and medical treatments
- having an iron deficiency or vitamin B deficiency
- viruses, such as human papillomavirus (HPV)
About 4 in every 10 people who get mouth ulcers have a family member who also gets them.
When should I see my doctor?
See your doctor if your mouth ulcer lasts longer than 2 weeks or keeps coming back. This may be a sign of a more serious problem.
See your doctor if you have a mouth ulcer as well as other symptoms, such as:
- weight loss or stomach pain
- a fever (a temperature of 38℃ or higher)
- mucus or blood in your stool (poo)
- changes in the skin in your mouth
- ulcers around your anus (bottom)
- changes in your mouth that you are worried about
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How are mouth ulcers diagnosed?
Your doctor or dentist can usually diagnose a mouth ulcer by looking at it.
They may also ask you questions about:
- your symptoms
- your diet
- your medical history
- any medicines you regularly take
- any injuries that may have caused the mouth ulcer
If your doctor or dentist thinks your mouth ulcer is infected, they may take a swab from the ulcer to test for bacteria. This helps them understand what is causing the infection and how to best treat it.
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How are mouth ulcers treated?
Most mouth ulcers heal without treatment after 1 to 2 weeks.
Self-care at home
Here are some tips to help look after yourself if you have a mouth ulcer:
- Try not to touch the ulcer. Touching the ulcer can disturb the healing process and can also spread infection. If you do need to touch the area, make sure to wash your hands before and after.
- Use a soft toothbrush to clean your teeth. If your sores are so painful that you can't brush your teeth, use a mouthwash instead. Avoid using mouthwashes that contain alcohol.
- Rinsing your mouth with salt water can help relieve pain and reduce the chance of infection. Make a saltwater rinse by mixing one teaspoon of salt into a cup of water. Take a mouthful of the liquid, hold it in your mouth so it covers the affected area and then spit it out. Repeat this process a few times a day.
- Eat soft foods.
- Avoid hot foods, hot drinks and spicy foods.
- If your mouth is very sore, try drinking through a straw.
Medicines for mouth ulcers
You can help manage your discomfort by using an anaesthetic mouth gel on the area. This will numb the pain but will not heal the ulcer. You can buy anaesthetic mouth gel over-the-counter from pharmacies.
If you are experiencing a lot of pain from your mouth ulcer, ask your doctor or pharmacist about other pain-relief options.
Vitamin B12 supplements may help your mouth ulcer heal. Before taking a supplement, ask your doctor if it's right for you.
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What are the complications of mouth ulcers?
Most mouth ulcers heal without scarring. However, bigger ulcers can leave scars.
If you have recurrent mouth ulcers, you may need to use a cream on them when they are active (flare-up). Sometimes, immunomodulatory treatment (medicine to help your immune system) is recommended, however this is rare.
For most people with recurrent mouth ulcers, your symptoms will become milder and happen less often over time.
Can mouth ulcers be prevented?
There are some ways to reduce your chance of getting a mouth ulcer, such as:
- maintaining a healthy diet
- reducing or managing your stress
- avoiding foods and drinks that trigger ulcers
- making sure your braces or dentures fit well
Resources and support
Read more about dental and mouth care.
The Cancer Australia page offers tips on how to manage mouth sores.
You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with you 24 hours a day, 7 days a week.