Mouth sores are one of the most common oral health complaints, affecting roughly 20% of the population at any given time. They are painful, disruptive, and often appear at the worst possible moments. Most resolve on their own within one to two weeks. But some persist longer, recur frequently, or signal something that warrants a closer look. Knowing the difference, and knowing when to seek care, helps you manage mouth sores more effectively and catch anything that should not be ignored.
At Lifetime Smiles in Bellevue, WA, Dr. Michael Beke, DMD, and our team evaluate oral tissue changes at every comprehensive visit, including checking for sores, lesions, and anything that does not look or feel right. If you have a mouth sore that has lasted more than two weeks or keeps coming back, contact our office to schedule an evaluation.
Canker Sores vs. Cold Sores: An Important Distinction
These two types of mouth sores are often confused, but they are caused by entirely different things and require different responses.
Canker sores (aphthous ulcers) appear inside the mouth, on the soft tissue of the cheeks, tongue, gums, or lips. They are not contagious. Canker sores are not caused by a virus, and they cannot be spread through kissing or sharing utensils. Their exact cause is not fully understood, but triggers include stress, tissue injury, certain foods, hormonal changes, and nutritional deficiencies.
Cold sores are caused by the herpes simplex virus type 1 (HSV-1) and are highly contagious. They appear on or around the outside of the lips, not on the soft tissue inside the mouth. Cold sores often begin with a tingling or burning sensation before the blister forms. Antiviral medications can shorten their duration and reduce recurrence.
If your sore is inside your mouth, on soft tissue, and not on the lip surface, it is most likely a canker sore. If it is on or outside the lip border and you feel a tingling sensation before it appears, it is more likely a cold sore. When in doubt, have it evaluated.
Types of Canker Sores
Not all canker sores are the same. There are three recognized types, distinguished by their size, frequency, and healing time.
Minor canker sores are the most common type. They are small, oval-shaped ulcers, typically less than one centimeter in diameter, with a white or yellowish center and a red border. They heal on their own within one to two weeks and rarely leave scars.
Major canker sores are larger, deeper, and more painful. They can exceed one centimeter in diameter, may have irregular edges, and can take four to six weeks to heal. Major canker sores may leave scarring in some cases and tend to recur. They are more commonly associated with systemic health conditions and may warrant investigation if they appear frequently.
Herpetiform canker sores are not caused by the herpes virus despite the name. They appear as clusters of pinpoint-sized ulcers, sometimes 10 to 100 at a time, that can merge into larger irregular sores. They heal in one to two weeks but are painful and tend to recur.
Where Do Canker Sores Come From?
Canker sores do not have a single cause. Research points to a combination of factors that vary from person to person. Some of the most commonly identified triggers include:
- Tissue injury: Accidental biting of the cheek or tongue, aggressive brushing, or irritation from braces or dental appliances can all initiate a sore.
- Nutritional deficiencies: Low levels of vitamin B12, zinc, folate, and iron are associated with increased canker sore frequency.
- Stress: Physical or emotional stress is one of the most consistently reported triggers in patients who experience recurrent sores.
- Food sensitivities: Acidic foods such as citrus and tomatoes, as well as foods containing sodium lauryl sulfate (a common toothpaste ingredient), can trigger sores in susceptible individuals.
- Hormonal changes: Some women experience canker sores predictably in connection with their menstrual cycle.
- Systemic conditions: Conditions including celiac disease, Crohn’s disease, and some autoimmune disorders are associated with recurrent aphthous ulcers.
Tips to Minimize Discomfort While a Sore Heals
Most canker sores heal without treatment, but the pain can be significant while they are active. Several strategies can help reduce discomfort during the healing period.
Topical anesthetics available without a prescription, such as those containing benzocaine, can provide temporary numbing relief. Antimicrobial or anti-inflammatory mouth rinses can reduce irritation and support the healing environment. Avoiding acidic, spicy, and rough-textured foods while a sore is active prevents additional irritation. Rinsing with a warm salt water solution several times daily can help keep the area clean and reduce inflammation.
For frequent or severe canker sores, a dentist may prescribe a topical corticosteroid, an antimicrobial rinse, or another targeted treatment to speed healing and reduce recurrence.
How to Prevent Canker Sores
While there is no guaranteed way to prevent canker sores entirely, reducing your exposure to known triggers can lower how often they occur and how severe they are when they do.
Choose a toothpaste that does not contain sodium lauryl sulfate if you notice a connection between brushing and sore development. Eat a balanced diet and consider supplementing vitamin B12, zinc, and iron if you tend toward deficiency. Manage stress through consistent sleep, physical activity, and whatever relaxation practices work for you. If you wear braces or a dental appliance that rubs against soft tissue, talk to our team about wax or adjustments that can reduce friction.
When to See Your Dentist About a Mouth Sore
Most canker sores heal within two weeks without medical intervention. These situations call for an evaluation rather than waiting it out:
- A sore that has not healed after two weeks
- Sores that are unusually large or painful compared to what you have experienced before
- Sores that recur so frequently there is little time between outbreaks
- A sore accompanied by fever or swollen lymph nodes
- Difficulty eating, drinking, or swallowing because of a sore
- Any growth, lump, or discoloration on the tongue or oral tissue that was not there before
Persistent sores that do not heal on schedule are among the early warning signs of oral cancer, which is far more treatable when caught early. Regular comprehensive dental exams at Lifetime Smiles include a thorough oral tissue check at every visit.
Frequently Asked Questions About Mouth Sores
Are canker sores contagious?
No. Canker sores are not caused by a virus and cannot be spread through kissing, sharing food or drinks, or any form of contact. Cold sores, by contrast, are caused by the herpes simplex virus and are contagious. If you are unsure which type you have, have a dentist evaluate it, especially if it appears outside the mouth or on the lip border.
How long does a typical canker sore last?
Minor canker sores typically heal within one to two weeks without treatment. Major canker sores can take four to six weeks and may leave some scarring. If a sore has not healed within two weeks, it should be evaluated by a dentist to rule out other causes, including oral cancer.
What foods should I avoid when I have a canker sore?
Avoid acidic foods such as citrus fruits, tomatoes, and vinegar-based foods, as well as spicy dishes and anything with sharp or rough textures that could physically irritate the sore. Alcohol-containing mouth rinses can also aggravate healing tissue. Soft, bland foods are easiest to eat while a sore is active.
Can stress really cause mouth sores?
Yes. Stress is one of the most consistently reported triggers for canker sore outbreaks. Physical stress, such as illness or sleep deprivation, and emotional stress both appear to lower the threshold for sore development in people who are susceptible. Managing stress through regular sleep, physical activity, and relaxation practices may help reduce how often sores occur.
When should a mouth sore be evaluated for oral cancer?
Any sore that does not heal within two weeks should be evaluated. Additional warning signs include a sore that bleeds without reason, a lump or thickening anywhere in the mouth, persistent pain or numbness, and difficulty chewing or swallowing. Oral cancer is most treatable when caught early, which is why routine dental exams with soft tissue screening are so important.
Dr. Michael Beke, DMD, and the team at Lifetime Smiles in Bellevue, WA, perform a thorough oral tissue evaluation at every comprehensive exam, checking for any changes in the soft tissues of the mouth, tongue, and throat. If a sore or lesion warrants attention, we will discuss next steps clearly and without delay.
If you have a mouth sore that has persisted beyond two weeks or that keeps returning, do not wait. Contact our Bellevue office to schedule an evaluation.