Why Do I Keep Getting Canker Sores?
Recurring canker sores are usually triggered by minor mouth injuries, stress, certain foods, toothpaste ingredients, hormone changes or low levels of nutrients like iron, B12, folate or zinc. They’re very common, not contagious and usually heal on their own in 1 to 2 weeks. Sores that keep coming back often have a fixable trigger, such as a sharp tooth edge or worn filling that a dentist can smooth through restorative care.
Canker sores are small, but they hurt far more than their size suggests. Eating, talking and brushing can all sting.
The good news is that most are harmless. For painful outbreaks, laser treatment in Tillsonburg can sometimes ease pain and help sores heal faster.
A sore that’s unusually large, lasts more than 2 weeks or comes with fever or swollen glands is different. That needs a prompt look, and the dental emergency in Tillsonburg team can see you quickly if pain is severe.
If you’d like to know who you’ll be seeing, the meet our doctors page introduces the team. When you’re ready, you can book an appointment online.
What is a canker sore?
A canker sore (aphthous ulcer) is a shallow, round or oval sore inside the mouth. It usually has a white, yellow or grey centre with a red border. They appear on the inside of the cheeks and lips, on or under the tongue and on the soft palate.
Canker sores aren’t caused by a virus and can’t be spread to other people.
Types of canker sores
| Type | Size | Healing time | How common |
|---|---|---|---|
| Minor | Under 1 cm | About 1 to 2 weeks, no scar | Most common |
| Major | Over 1 cm, deeper | Several weeks, may scar | Less common |
| Herpetiform | Many tiny sores in clusters | About 1 to 2 weeks | Rare |
Canker sore or cold sore?
| Canker sore | Cold sore | |
|---|---|---|
| Location | Inside the mouth | Usually on or around the lips |
| Cause | Triggers like injury, stress, food | Herpes simplex virus |
| Contagious | No | Yes |
| Look | White or yellow centre, red border | Fluid-filled blisters that crust |
| Early sign | Tingling or burning spot | Tingling, then blisters |
Why do I keep getting canker sores?
Mouth injuries
Biting your cheek, brushing too hard, a sharp chip, a rough filling edge, braces or a poorly fitting denture can all start a sore. If they always appear in the same spot, look for something rubbing there.
Stress and lack of sleep
Many people notice outbreaks during exams, deadlines or busy stretches.
Food triggers
Acidic and spicy foods are common: citrus, tomatoes, pineapple, vinegar, chocolate, coffee, nuts and chips with sharp edges.
Toothpaste and mouthwash
Sodium lauryl sulfate (SLS), a foaming agent in many toothpastes, is linked to more frequent sores in some people. Strong alcohol-based mouthwashes can also irritate.
Nutrient deficiencies
Low iron, vitamin B12, folate or zinc can make sores more frequent.
Hormones
Some people get sores around their period.
Health conditions
Frequent or severe sores can be linked to celiac disease, inflammatory bowel disease, Behcet’s disease, immune system conditions and some medications.
Genetics
Recurring canker sores often run in families.
How do you treat a canker sore at home?
- Rinse with salt water or baking soda (half a teaspoon in a cup of warm water) a few times a day.
- Use an over-the-counter numbing gel or protective paste from a pharmacy.
- Avoid acidic, spicy and crunchy foods until it heals.
- Switch to an SLS-free toothpaste and a soft toothbrush.
- Use a straw for acidic drinks.
- Ask a pharmacist about suitable pain relief.
- Cover sharp edges with orthodontic wax if braces or a chipped tooth is the cause.
How can a dentist help?
- Smoothing sharp teeth, fillings or crowns that keep causing sores
- Adjusting dentures or orthodontic appliances
- Prescribing a protective paste or a medicated rinse
- Laser treatment to reduce pain for some sores
- Checking whether the sore is something other than a canker sore
- Referring you to your doctor for blood tests if deficiencies or other conditions are suspected
Myths about canker sores
“Canker sores are contagious.”
They aren’t. Cold sores are contagious. Canker sores aren’t caused by an infection that spreads between people.
“Putting salt directly on it helps.”
It mostly just hurts. A diluted salt water rinse is gentler and works better.
“Frequent canker sores mean poor hygiene.”
They’re more about triggers and your immune response than how clean your mouth is.
“A dental visit for a mouth sore will hurt.”
An exam is quick and gentle. Treatments like protective pastes or a laser are designed to reduce pain, not add to it.
A 28-year-old who got sores in the same spot every month had a chipped molar rubbing her cheek. Smoothing the edge ended the pattern.
A 35-year-old with frequent sores switched to an SLS-free toothpaste and saw outbreaks drop noticeably over 3 months.
A 42-year-old with sores and fatigue had blood tests through his doctor that showed low iron. Treating it reduced his sores.
Common mistakes
- Using harsh mouthwashes that sting and dry the mouth
- Ignoring a rough tooth that keeps rubbing
- Assuming a sore that hasn’t healed in weeks is “just a canker sore”
- Not mentioning frequent sores to a dentist or doctor
- Poking or picking at the sore
How can you prevent canker sores?
- Use a soft toothbrush and gentle technique
- Try an SLS-free toothpaste
- Keep a food diary to spot personal triggers
- Manage stress and get enough sleep
- Eat a balanced diet, and ask your doctor about testing if sores are frequent
- Get sharp teeth and rough dental work fixed
- Use orthodontic wax on braces
Which toothpastes and rinses are gentler on canker sores?
| Product | Gentler choice | Why |
|---|---|---|
| Toothpaste | SLS-free with fluoride | Less irritation to delicate tissue |
| Mouthwash | Alcohol-free | Alcohol stings and dries the mouth |
| Toothbrush | Soft or extra-soft bristles | Fewer scrapes on cheeks and gums |
| Floss | Smooth, waxed floss | Slides easily without cutting gums |
| Rinse | Salt water or baking soda solution | Simple, soothing and cheap |
Do canker sores affect children?
Yes. Kids and teens get canker sores often, especially when they bite their cheek, have braces or are going through growth spurts and stressful school periods. The same gentle care applies: salt water rinses, soft foods and avoiding acidic snacks. Frequent sores in children, or sores with fever, should be checked by a dentist or doctor, because some childhood conditions cause similar mouth ulcers.
What about braces and canker sores?
New braces are a classic trigger. Brackets and wires rub the inside of the lips and cheeks until the tissue toughens up, usually over a few weeks. Orthodontic wax over the rubbing spot gives quick relief. If a wire is poking out, call your orthodontist, since a small trim usually solves the problem.
How do you know if a mouth sore is something more serious?
Most mouth sores are harmless. A few signs suggest something else is going on:
- A sore that’s hard or raised at the edges
- A red or white patch that doesn’t heal
- A sore that doesn’t hurt but doesn’t go away
- Numbness in the area
- Smoking or heavy alcohol use, which raise oral cancer risk
Your dentist checks the soft tissues of your mouth at every exam. That routine screening is one of the most useful parts of a checkup, even when your teeth feel fine.
Questions to ask your dentist
- Is this a canker sore or something else?
- Could a tooth, filling or appliance be causing it?
- Would a protective paste or laser treatment help?
- Should I talk to my doctor about blood tests?
- Which toothpaste would you recommend for me?
What foods are easiest to eat with a canker sore?
- Yogurt, smoothies and milk
- Oatmeal and soft cereals
- Mashed potatoes and soft vegetables
- Scrambled eggs
- Bananas and melon
- Soft pasta with mild sauces
Does stress really cause canker sores?
Stress doesn’t cause every sore, but it’s one of the most common triggers people report. When you’re stressed, you may sleep less, eat differently, bite your cheek or clench your teeth, and your immune system responds differently. All of these can make outbreaks more likely.
Simple habits help: regular sleep, short walks, staying hydrated and taking breaks from screens. If sores show up around every stressful deadline, that pattern is worth noting in your symptom diary.
How long should you wait before seeing a dentist?
| Situation | When to book |
|---|---|
| Single small sore, improving | No visit needed, mention it at your next checkup |
| Sore in the same spot every time | Book a check to look for a sharp edge |
| Sore not healing after 2 weeks | Book within a few days |
| Very painful, large or multiple sores | Book soon, same week |
| Sores with fever or trouble eating and drinking | Same-day care |
Keeping a simple note of when sores appear, where they are and what you’d eaten makes the visit far more productive.
Can canker sores be prevented with supplements?
If a blood test shows a deficiency in iron, B12, folate or zinc, correcting it can reduce how often sores appear. Without a confirmed deficiency, supplements may not help much, and some can cause side effects. It’s best to ask your doctor before starting any supplement, especially if you take other medications or are pregnant. A balanced diet with plenty of fruits, vegetables, whole grains and protein supports healthy mouth tissue for most people.
Small changes, tracked over a few months, usually reveal what your personal triggers are.
Mouth sore care at Family Dentistry on Brock
If you need a dentist in Tillsonburg who will look at the cause of repeat sores, Family Dentistry on Brock is one of the most trusted clinics in town, with a 5.0 Google rating from 252+ patient reviews.
New patients and CDCP patients are welcome. Services include dental implants, clear aligners, restorative care, dental veneers, laser treatment, teeth whitening, dental emergency care, sedation dentistry, dental surgery and orthodontics.
Weekday hours extend to 7:00 PM on Mondays, with Saturdays by appointment. Call +1 519-900-5640, email info@familydentistryonbrock.com, or visit 49 Brock St E, Tillsonburg, ON N4G 1Z7.
Care is provided by licensed dental professionals registered with the Royal College of Dental Surgeons of Ontario (RCDSO).
Frequently asked questions
How long do canker sores last?
Most minor canker sores heal in 1 to 2 weeks without scarring. Larger ones can take several weeks and should be checked by a dentist.
Are canker sores contagious?
No. Canker sores aren’t contagious. Cold sores, which usually appear on the lips, are caused by a virus and can spread.
What vitamin deficiency causes canker sores?
Low levels of vitamin B12, iron, folate and zinc are linked to recurring canker sores. Your doctor can check these with a blood test.
Can toothpaste cause canker sores?
Toothpaste with sodium lauryl sulfate may trigger sores in some people. Switching to an SLS-free toothpaste often helps.
When should I see a dentist for a canker sore?
See a dentist if a sore lasts more than 2 weeks, is very large, keeps coming back often, or comes with fever or other symptoms.
Conclusion
Canker sores are common, not contagious and usually heal within 1 to 2 weeks.
Repeat sores often have a trigger, like a sharp tooth, toothpaste ingredient, stress or a nutrient deficiency.
Finding and fixing that trigger is the best way to have fewer and milder outbreaks.
