What Are Canker Sores?
Canker sores, known clinically as aphthous ulcers, are shallow open wounds inside the mouth. They typically appear as round or oval spots with a white or yellowish center and a red border. Unlike cold sores, canker sores do not appear on the outside of the lips and are not caused by a virus.
There are three types of canker sores. Minor canker sores are the most common, measuring less than 1 centimeter across, and heal within 1 to 2 weeks without scarring. Major canker sores are larger, deeper, and can take up to 6 weeks to heal, sometimes leaving a scar. Herpetiform canker sores are rare, appearing as clusters of tiny ulcers that may merge into one larger sore.
Canker sores affect roughly 20% of the general population at some point. They are more common in women, teenagers, and young adults. While they are not dangerous, the pain can interfere with eating, drinking, and speaking.
What Causes Canker Sores?
The exact cause of canker sores is not fully understood. Research suggests they result from a combination of factors rather than a single trigger. Knowing your personal triggers can help you reduce how often they occur.
Common Triggers
- Mouth injuries: Biting the inside of your cheek, brushing too hard, dental work irritation, or sports injuries can trigger a canker sore at the site of the trauma.
- Food sensitivities: Acidic or spicy foods such as citrus fruits, tomatoes, pineapple, and hot peppers are frequent triggers for some people.
- Sodium lauryl sulfate (SLS): This foaming agent found in many toothpastes has been linked to canker sore outbreaks. Switching to an SLS-free toothpaste may help.
- Stress and lack of sleep: Emotional stress and sleep deprivation are among the most commonly reported triggers.
- Hormonal changes: Some women experience canker sores in connection with their menstrual cycle.
Underlying Conditions Linked to Frequent Canker Sores
If you get canker sores frequently, your doctor or dentist may want to check for underlying conditions. Nutritional deficiencies in iron, vitamin B12, zinc, or folate are a common and treatable cause. Celiac disease, Crohn's disease, and other inflammatory bowel conditions are also associated with recurrent aphthous ulcers.
- Vitamin B12, iron, zinc, or folate deficiency
- Celiac disease
- Inflammatory bowel disease (Crohn's disease, ulcerative colitis)
- Immune system disorders such as Behcet's disease
- HIV/AIDS or other immunocompromising conditions
Home Remedies for Canker Sores
For most minor canker sores, home treatment is enough to manage pain and support healing. These remedies do not cure canker sores instantly, but they can reduce discomfort and may shorten the healing timeline by a few days.
Salt Water Rinse
Dissolve half a teaspoon of salt in 8 ounces of warm water. Swish the solution around your mouth for 15 to 30 seconds, then spit it out. Repeat 2 to 3 times per day. Salt water helps reduce bacteria around the sore and can temporarily relieve pain. It may sting on contact, but the discomfort fades quickly.
Baking Soda Paste or Rinse
Mix a small amount of baking soda with water to form a thick paste. Apply it directly to the canker sore and leave it on for a few minutes before rinsing. Alternatively, dissolve one teaspoon of baking soda in half a cup of warm water and use it as a mouth rinse. Baking soda helps neutralize acids in the mouth and may reduce irritation.
Over-the-Counter Gels and Rinses
Benzocaine-based products (such as Orajel or Anbesol) numb the area on contact and can make eating and drinking less painful. Apply directly to the sore up to 4 times per day. Hydrogen peroxide rinses (diluted to half strength with water) can help keep the sore clean. Some people also find relief from OTC protective pastes like Orabase, which form a barrier over the ulcer to shield it from food and saliva.
Other Home Options
- Honey: Applying a small amount of raw honey to the sore several times a day may reduce pain and sore size. A small study published in Quintessence International found that honey application reduced canker sore pain and healing time compared to no treatment.
- Ice chips: Holding ice against the sore can temporarily numb the pain.
- Avoiding trigger foods: Stay away from acidic, spicy, or sharp-edged foods (chips, crackers) until the sore heals.
- Milk of magnesia: Dabbing a small amount on the sore 3 to 4 times per day may coat and soothe the ulcer.
Prescription Treatments for Canker Sores
When canker sores are large, extremely painful, slow to heal, or keep coming back, a dentist or oral surgeon may prescribe stronger treatments. These options are typically reserved for major aphthous ulcers or cases where over-the-counter remedies are not providing relief.
Debacterol (Chemical Cautery)
Debacterol is a topical solution applied directly to the canker sore by a dentist or oral surgeon. It chemically cauterizes the ulcer, sealing the nerve endings. Many patients report significant pain relief within minutes of a single application. The treated sore typically heals faster than it would on its own.
Corticosteroid Rinses and Topical Pastes
Prescription corticosteroid mouth rinses (such as dexamethasone) reduce inflammation and pain. Topical corticosteroid pastes like fluocinonide (Lidex) or triamcinolone acetonide can be applied directly to the sore. These medications work best when started at the first sign of a canker sore. They reduce the severity and duration of the outbreak.
Other Prescription Options
For patients with frequent, severe canker sores that do not respond to topical treatments, a specialist may consider systemic medications. Colchicine, a drug originally used for gout, has shown some benefit for recurrent aphthous ulcers. In rare, severe cases, immunomodulators may be considered. These systemic options require careful monitoring and are typically managed by a specialist.
How to Prevent Canker Sores
While there is no guaranteed way to prevent all canker sores, certain habits can reduce how often they occur and how severe they are.
- Switch to an SLS-free toothpaste if you notice sores developing after brushing.
- Use a soft-bristled toothbrush to reduce mouth injuries from brushing.
- Keep a food diary to identify personal trigger foods, then avoid them.
- Manage stress through regular sleep, exercise, or stress-reduction techniques.
- If you wear braces or dental appliances, ask your orthodontist about dental wax to cover sharp edges.
- Address nutritional gaps. A blood test can check for deficiencies in iron, B12, zinc, and folate.
When to See an Oral Surgeon or Specialist
Most canker sores do not require professional treatment. However, certain signs indicate that you should see a dentist or an oral surgeon for evaluation.
Schedule an appointment if a canker sore lasts longer than 3 weeks, is larger than 1 centimeter across, is spreading or getting worse, causes a fever, or makes it too painful to eat or drink. Frequent outbreaks (more than 3 to 4 times per year) also warrant a professional evaluation to check for underlying causes.
An oral surgeon can perform a biopsy if a persistent mouth sore does not look like a typical canker sore. While canker sores are not cancerous, other oral lesions can resemble them. Any sore that does not heal within 3 weeks should be evaluated to rule out oral cancer or other conditions.
Find an Oral Surgeon Near You
If you have canker sores that keep coming back or will not heal, a specialist can help identify the cause and recommend targeted treatment. Search the My Specialty Dentist directory to find a board-certified oral surgeon in your area.
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