Recurrent Mouth Ulcers (Aphthous Stomatitis)

If you have a single new ulcer and want to know what might be causing it, see our guide to mouth ulcer causes and when to worry. This page explains recurrent canker sores as a condition.

What happens in recurrent aphthous stomatitis

The exact cause is unknown. The best explanation is that, in susceptible people, immune cells (T cells) attack the mouth lining in response to a minor trigger. A small area becomes inflamed and breaks down into an ulcer. Within days the immune reaction settles, and the lining heals over 1 to 2 weeks.

There is a strong genetic component: about 40 percent of people with recurrent ulcers have a family history.

Types of aphthous ulcers

Despite the name, herpetiform ulcers are not caused by herpes.

Triggers

• minor mouth injury: biting, brushing, dental work, braces
• stress and lack of sleep
• hormonal changes, often in the days before a period
• toothpastes with sodium lauryl sulfate (SLS)
• certain foods, such as chocolate, coffee, nuts, citrus, tomatoes and spicy foods, in some people
• stopping smoking (ulcers often increase temporarily)

Linked health conditions

Most people with canker sores are otherwise healthy. Doctors look for an underlying condition when ulcers start in adulthood, are severe, or come with other symptoms:

• Deficiencies: iron deficiency anemia, low vitamin B12 or folate, and sometimes zinc. Correcting these can stop ulcers.
• Celiac disease: a gluten-free diet may reduce ulcers.
• Crohn's disease and ulcerative colitis.
• Behçet's disease: recurrent mouth ulcers plus genital ulcers, eye inflammation and skin lesions.
• HIV: large, persistent ulcers.
• PFAPA syndrome in young children: periodic fever, mouth ulcers, sore throat and swollen neck glands every 3 to 6 weeks.
• Cyclic neutropenia: ulcers with recurring low white cell counts.

Diagnosis

Recurrent aphthous stomatitis is diagnosed from the typical appearance and pattern. There is no specific test. For frequent, severe or adult-onset ulcers, doctors usually check:

• complete blood count
• ferritin (iron stores), vitamin B12 and folate
• celiac antibodies (tTG-IgA)
• inflammatory markers and other tests guided by symptoms

A biopsy is done for any ulcer that does not heal within 3 weeks or looks atypical, to exclude cancer and other diseases.

Treatment

No treatment cures the tendency, but many reduce pain, shorten episodes and lower frequency.

Pharmacy treatments

• Protective pastes and films that coat the ulcer and reduce pain while eating.
• Numbing gels with benzocaine or lidocaine, used as directed. Benzocaine is not suitable for children under 2.
• Antiseptic mouthwash such as chlorhexidine reduces secondary infection. It can stain teeth temporarily.
• Saltwater rinses.

Prescription treatments

• Topical steroids as mouthwashes, lozenges or pastes, applied early in an episode, reduce pain and healing time. These are the mainstay for frequent ulcers.
• Doxycycline mouth rinse in adults for herpetiform ulcers.
• Systemic treatments such as colchicine, short courses of oral steroids or other immune-modulating medicines are reserved for severe, disabling disease and Behçet's, under specialist care.

Treat underlying causes

Correcting iron, B12 or folate deficiency, treating celiac disease or IBD, and adjusting medicines can greatly reduce or stop ulcers.

Prevention

• Use an SLS-free toothpaste.
• Brush with a soft toothbrush and avoid injury from hard or sharp foods.
• Keep a food diary to spot personal triggers.
• Manage stress and get enough sleep.
• Ask a dentist to fix sharp teeth, rough fillings or rubbing appliances.

Outlook

Recurrent canker sores are a nuisance but not dangerous. Episodes tend to become less frequent with age, and many people stop getting them by their 30s or 40s.

Frequently asked questions

Why do I keep getting mouth ulcers?

Recurring canker sores tend to run in families and are triggered by minor injury, stress, hormones, certain foods or SLS toothpaste. In some people, low iron, B12 or folate, celiac disease or Crohn's disease are the cause. Frequent ulcers deserve a blood test.

How do you get rid of a mouth ulcer fast?

Protective pastes, numbing gels and antiseptic mouthwashes ease pain, and avoiding spicy and acidic food helps healing. A prescription steroid mouthwash or paste started at the first tingle can shorten an ulcer. Most still take about a week to heal fully.

Are canker sores the same as cold sores?

No. Canker sores occur inside the mouth, are not contagious and are not caused by a virus. Cold sores are caused by the herpes simplex virus, usually appear on or around the lips as blisters, and are contagious.

Can stress cause mouth ulcers?

Yes. Stress and lack of sleep are well-recognized triggers for canker sores in people who are prone to them. Many people notice ulcers around exams, deadlines or emotional upset. Managing stress can reduce how often they appear.