ConditionMouth & teeth
Aphthous Stomatitis (Canker Sores)
Aphthous stomatitis is a common condition in which painful, round, shallow ulcers called canker sores keep appearing inside the mouth. Each sore has a white or yellow base and a red rim and usually heals in 1 to 2 weeks without a scar. It is not contagious and not caused by the herpes virus. Triggers include minor injury, stress, certain toothpastes and hormonal changes. Frequent or severe outbreaks can be linked to vitamin deficiencies, celiac disease, inflammatory bowel disease or Behçet's disease.
Also called: Canker sores, recurrent aphthous stomatitis, recurrent aphthous ulcers, aphthae, mouth ulcers
At a glance
- What it is
- Recurring, painful, non-contagious ulcers inside the mouth.
- How common
- Affects about 1 in 5 people at some point. Usually starts in childhood or the teens.
- Types
- Minor (most common), major (large, slow to heal) and herpetiform (many tiny ulcers).
- Triggers
- Mouth injury, stress, sodium lauryl sulfate toothpaste, certain foods, hormones, deficiencies.
- Treatment
- Protective pastes, numbing gels, antiseptic rinses, steroid gels, and treating any underlying cause.
When to get help
See a doctor within a day or two
- Mouth ulcers with a high fever above 39 °C (102 °F), a widespread rash, or sores on the eyes or genitals
- Sores so painful that you or your child cannot drink enough fluids
- A sore that is spreading rapidly or bleeding heavily
Book a routine appointment
- A mouth ulcer that has not healed after 3 weeks
- Ulcers larger than 1 cm, or that leave scars
- Outbreaks almost constantly, or more often than every few weeks
- Mouth ulcers with diarrhea, weight loss, joint pain, eye inflammation or genital ulcers
- A painless ulcer, or a hard or raised ulcer, especially if you smoke or drink heavily
Usually safe to manage at home
- A single small sore with a red rim that started after biting your cheek or eating something sharp
- Your usual canker sores that heal within 2 weeks
What canker sores look like
Canker sores appear on the soft, moveable lining of the mouth: inside the lips and cheeks, under or on the sides of the tongue, the floor of the mouth and the soft palate. They rarely appear on the gums or hard palate, which helps tell them apart from herpes sores. A tingling or burning feeling often comes 1 to 2 days before the sore appears.
Types of aphthous stomatitis
| Type | Share of cases | Size and number | Healing |
|---|---|---|---|
| Minor | About 80 in 100 | Under 1 cm, 1 to 5 at a time | 7 to 14 days, no scar |
| Major | About 10 to 15 in 100 | Over 1 cm, deep, 1 or 2 at a time | 2 to 6 weeks or more, may scar |
| Herpetiform | About 5 to 10 in 100 | 1 to 3 mm, dozens at once, may merge | 7 to 14 days |
Despite the name, herpetiform ulcers are not caused by herpes. They only resemble it.
Canker sores vs cold sores
| Canker sores | Cold sores (oral herpes) | |
|---|---|---|
| Cause | Immune reaction, not an infection | Herpes simplex virus |
| Location | Inside the mouth, soft lining | Outside, on or around the lips. Inside the mouth on gums and hard palate |
| Appearance | Round ulcer, white-yellow base, red rim | Cluster of fluid-filled blisters that crust |
| Contagious | No | Yes |
See oral herpes for cold sores.
Causes and triggers
The exact cause is unknown. It appears to be an immune reaction in which white blood cells attack the mouth lining. A family history is common. Known triggers include:
- minor injury: biting the cheek, sharp food, dental work, braces, or vigorous brushing
- sodium lauryl sulfate (SLS), a foaming agent in many toothpastes
- stress and lack of sleep
- hormonal changes, with some people getting sores around their period
- foods: chocolate, coffee, nuts, citrus, tomatoes, strawberries, spicy or acidic foods in some people
- stopping smoking: smokers get fewer canker sores, and outbreaks can increase after quitting (this is not a reason to keep smoking)
Underlying conditions
Recurrent or severe ulcers can be a sign of:
- nutritional deficiencies: iron, vitamin B12, folate or zinc
- celiac disease, which may have few other symptoms
- Crohn's disease and ulcerative colitis
- Behçet's disease: recurrent mouth and genital ulcers, eye inflammation and skin lesions
- HIV and other causes of a weakened immune system
- cyclic neutropenia and PFAPA syndrome in children (periodic fever, mouth ulcers, sore throat and swollen neck glands)
- medicines such as NSAIDs, nicorandil, beta blockers and some chemotherapy drugs
Diagnosis
A dentist or doctor diagnoses canker sores by their appearance and history. No test is needed for typical minor sores. For frequent, severe or unusual ulcers, tests may include:
- blood count, iron studies, B12, folate and zinc
- celiac antibody test
- tests for inflammatory bowel disease if there are bowel symptoms
- swab for herpes if the sores look atypical
- biopsy for an ulcer that does not heal within 3 weeks, to rule out other conditions including oral cancer
Treatment
There is no cure, but treatment eases pain and speeds healing.
Self-care
- Rinse with warm salt water or a baking soda rinse (1 teaspoon in half a cup of water).
- Avoid spicy, salty, acidic and crunchy foods while sores heal.
- Use a soft toothbrush and an SLS-free toothpaste.
- Apply ice chips or cold drinks to numb the area.
Over-the-counter options
- Protective pastes or gels that coat the ulcer.
- Numbing gels containing benzocaine or lidocaine. Do not use benzocaine in children under 2.
- Antiseptic mouthwashes such as chlorhexidine, which can shorten healing time. Long use may stain teeth.
- Pain relievers: acetaminophen (paracetamol) or ibuprofen, following the label dose.
Prescription treatments
- Topical steroids (gels, pastes or mouthwashes) applied early reduce pain and healing time.
- Steroid injections or tablets for major ulcers.
- Colchicine, dapsone, pentoxifylline or other medicines for severe, frequent ulcers under specialist care.
- Supplements to correct proven deficiencies. Vitamin B12 supplements may reduce outbreaks in some people even with normal levels.
- Treating underlying disease, such as a gluten-free diet for celiac disease.
Outlook
Canker sores tend to become less frequent with age and often stop by middle age. Most people manage with self-care and treatment of outbreaks. Major aphthae need more active treatment and specialist follow-up.
Frequently asked questions
What causes aphthous stomatitis?
The exact cause is not known. It seems to be an immune reaction in the mouth lining, often running in families. Triggers include mouth injury, stress, SLS toothpaste, certain foods and hormonal changes. Deficiencies and conditions such as celiac disease can make sores more frequent.
Are canker sores contagious?
No. Canker sores are not caused by an infection and cannot spread by kissing or sharing utensils. Cold sores, which are caused by the herpes virus, are contagious and usually appear on the lips rather than inside the mouth.
How do I get rid of canker sores fast?
Apply a protective or numbing gel, rinse with salt water or an antiseptic mouthwash, avoid spicy and acidic foods, and use an SLS-free toothpaste. A doctor or dentist can prescribe a steroid gel or rinse that shortens healing when started early.
Why do I keep getting canker sores?
Frequent canker sores are often due to a family tendency plus triggers like stress, mouth injury or SLS toothpaste. If they are very frequent or severe, ask your doctor to check for iron, B12 or folate deficiency, celiac disease, inflammatory bowel disease or Behçet's disease.
When is a mouth ulcer serious?
See a doctor or dentist if an ulcer lasts more than 3 weeks, is larger than 1 cm, is painless, hard or raised, or comes with fever, weight loss, diarrhea or genital ulcers. A non-healing ulcer needs a biopsy to rule out oral cancer.
Sources
This guide was written from current patient and clinical guidance, including:
- American Academy of Oral Medicine: Recurrent aphthous stomatitis
- American Dental Association (MouthHealthy): Canker sores
- MedlinePlus (US National Library of Medicine): Canker sore
- NHS: Mouth ulcers
- Mayo Clinic: Canker sore