A small sore inside the mouth that hurts every time you eat is very common. Most heal by themselves in one to two weeks, but some signs should not be ignored.
- An ordinary mouth ulcer heals by itself in about one to two weeks without scarring.
- Warm salt water rinses, soft cool food and avoiding spicy or sour food ease the sting.
- An ulcer lasting over three weeks, unusually large, hard-edged or recurring needs to be checked.
- A sharp tooth or rubbing denture is a local cause that can be fixed.
A mouth ulcer, or canker sore, is usually a small round or oval spot with a white-yellow centre and a red rim, found on the cheek, lip or tongue. It is not contagious, but it stings most when you eat hot, spicy or sour food.
What causes mouth ulcers?
There is often no fixed cause. Common triggers include:
- Biting the cheek or lip, or being rubbed by a sharp or chipped tooth or a denture.
- Stress, late nights and not enough sleep.
- A poor diet, or too much spicy, hot or sour food.
- A tendency to get them, which often runs in families.
If the sore keeps appearing in exactly the same spot, check whether a chipped tooth or denture is rubbing there, because treating the local cause means fewer repeat ulcers.
How long does a mouth ulcer take to heal?
Most small ulcers heal on their own in about one to two weeks without scarring. While you wait, you can ease the discomfort with simple steps:
- Rinse gently with warm salt water after meals.
- Eat soft, cool food and avoid spicy, salty, sour food and alcohol-based rinses for now.
- Brush gently with a soft brush and avoid pressing on the sore.
- Drink enough water and get enough sleep.
Please do not put products of unknown origin on the sore. If you need something, ask a dentist or doctor.
Signs that mean you should be checked early
See a dentist if any of these apply:
- The ulcer has lasted more than three weeks and has not healed.
- It is unusually large, has a hard raised edge, or hurts little but will not close.
- There are many ulcers at once, with fever or trouble swallowing.
- They keep coming back, or always appear where a sharp tooth or denture rubs.
The dentist will examine you to rule out other causes and deal with any tooth or denture that is rubbing the tissue.
Where to be seen
You can visit in person during working hours at 266A - 268, Đường 3 Tháng 2, Phường Hòa Hưng, Ho Chi Minh City, or call the hotline 028.3868.1097 (Zalo 082.299.3377) to ask about quieter hours. You may also like everyday habits that harm your teeth and bad breath: causes and what to do.
Frequently asked questions
Are mouth ulcers contagious?
An ordinary canker sore does not spread through shared food or kissing. If you also have a fever or ulcers spreading to many places, see a dentist or doctor.
When should I see a dentist about a mouth ulcer?
If it has not healed after about three weeks, is unusually large, has a hard edge or keeps coming back, get it checked.
Can a sharp tooth cause mouth ulcers?
Yes. A chipped or sharp tooth, or an ill-fitting denture, can rub the cheek or tongue and cause repeated ulcers. The dentist can adjust or treat the cause so they come back less often.