Aphthous Ulcer (Canker Sore)

What aphthous ulcers look like

• round or oval, shallow ulcers with a white, gray or yellow center and a red border
• on the non-keratinized (soft, moveable) lining of the mouth: inner cheeks, inner lips, under or on the sides of the tongue, floor of the mouth, soft palate
• a tingling or burning feeling may come a day before the ulcer appears
• painful, especially with spicy, salty or acidic foods

They do not usually occur on the gums attached to the teeth or the hard palate, which helps tell them apart from herpes.

Types

Herpetiform ulcers look like herpes but are not caused by the herpes virus.

Canker sore vs cold sore

Oral herpes can sometimes cause ulcers inside the mouth, especially on the gums and hard palate, and a first infection in a child often causes many painful ulcers with fever.

Causes and triggers

The exact cause is unknown, but involves a local immune reaction in people who are predisposed. Common triggers:

• minor injury: biting the cheek, sharp teeth, braces, rough brushing, dental work
• stress and lack of sleep
• toothpastes containing sodium lauryl sulfate (SLS)
• foods: citrus, tomatoes, chocolate, coffee, nuts, spicy foods
• hormonal changes around periods
• stopping smoking
• family history

Medical conditions linked to recurrent ulcers

• Nutritional deficiencies: iron (iron deficiency anemia), vitamin B12, folate and zinc
• Celiac disease
• Crohn's disease and ulcerative colitis
• Behçet's disease: recurrent mouth and genital ulcers, eye inflammation and skin lesions
• HIV and other immune problems
• Periodic fever syndromes in children (PFAPA: fever, mouth ulcers, sore throat, swollen glands every few weeks)
• Medicines: NSAIDs, nicorandil, beta-blockers and some chemotherapy

Diagnosis

Diagnosis is usually based on appearance and history. Blood tests are recommended for frequent, severe or unusual ulcers: blood count, iron studies, B12 and folate, and a celiac screen. A biopsy is needed for any ulcer that has not healed after 3 weeks, to rule out oral cancer, especially in smokers and heavy drinkers.

Treatment

There is no cure, but treatment eases pain and speeds healing.

Self-care

• rinse with warm salt water several times a day
• use a soft toothbrush and an SLS-free toothpaste
• avoid spicy, salty, acidic and crunchy foods while ulcers are present
• drink through a straw if eating is painful
• cover the ulcer with a protective paste

Over-the-counter treatments

• Anesthetic gels with benzocaine or lidocaine for pain. Benzocaine products should not be used in children under 2.
• Antiseptic mouthwash such as chlorhexidine to keep the area clean.
• Pain relievers such as acetaminophen (paracetamol) or ibuprofen at the label dose. Do not give aspirin to children or teenagers, and do not place aspirin on the gum, which burns the tissue.

Prescription treatments

• Topical steroids, such as dexamethasone mouthwash, triamcinolone paste or steroid sprays or lozenges, reduce pain and healing time when used early.
• Major or very frequent ulcers: oral steroids, colchicine, or other medicines under specialist care.
• Treating any deficiency or underlying disease often stops recurrences.

Prevention

• identify and avoid food and toothpaste triggers
• protect the mouth from injury, using orthodontic wax over braces
• manage stress and sleep
• treat iron, B12 or folate deficiency

Frequently asked questions

What causes canker sores?

Canker sores are caused by a local immune reaction in the mouth, often triggered by minor injury, stress, SLS toothpaste, acidic or spicy foods, or hormonal changes. Frequent sores can be linked to vitamin deficiencies, celiac disease or inflammatory bowel disease.

How long do canker sores last?

Most minor canker sores heal in 7 to 14 days. Major ulcers can take several weeks and may leave scars. Any mouth ulcer that lasts more than 3 weeks should be checked by a doctor or dentist.

Are aphthous ulcers contagious?

No. Aphthous ulcers are not caused by an infection and cannot be passed on by kissing or sharing utensils. Cold sores, caused by the herpes virus, are contagious.

What is the fastest way to heal a canker sore?

Applying a prescription steroid paste or mouthwash early, using an antiseptic rinse, avoiding irritating foods and using an SLS-free toothpaste can speed healing and reduce pain. Anesthetic gels give short-term relief.

When should I worry about a mouth ulcer?

See a doctor or dentist if an ulcer lasts more than 3 weeks, is painless and hard, keeps coming back, is very large, or comes with fever, weight loss, diarrhea, genital ulcers or eye problems.