Canker Sores: Causes, Treatment, and When to Worry

You've got a small, crater-like sore inside your mouth and it's ruining your day. Eating hurts. Talking hurts. Even thinking about citrus hurts. Welcome to the canker sore club — roughly 20% of the population gets them regularly.

The good news: canker sores are almost always harmless and heal on their own. The bad news: they're genuinely miserable while they last. Let's talk about what causes them, how to speed up healing, and the few situations where a mouth sore actually needs medical attention. Learn more about emergency dental care.

What Canker Sores Actually Are

Canker sores (aphthous ulcers) are small, shallow ulcers that form on the soft tissues inside your mouth — inner cheeks, inner lips, tongue, soft palate, base of the gums. They're round or oval, usually white or yellowish in the center with a red border, and they hurt way more than something that small should. Learn more about swollen gums.

Here's the thing people always get confused about: canker sores are NOT cold sores. They're completely different conditions. People mix them up constantly, so let's clear this up.

If your sore is inside your mouth and not on your lips, it's almost certainly a canker sore. If it's on your lip or the skin around your mouth and looks blistery, that's a cold sore and you need antiviral treatment.

"Recurrent aphthous stomatitis is the most common oral mucosal disease, affecting approximately 20% of the general population." — National Institute of Dental and Craniofacial Research

Three Types of Canker Sores

Minor canker sores. The most common type. Small (under 1 cm), round, and heal within 1-2 weeks without scarring. You'll get one or a few at a time. Annoying but manageable.

Major canker sores. Bigger than 1 cm, deeper, irregularly shaped. These take 6 weeks or longer to heal and can leave scars. If you're getting major canker sores, you should be seeing a dentist or doctor about them. They're miserable.

Herpetiform canker sores. Despite the name, these have nothing to do with herpes. They appear as clusters of tiny sores (10-100 at once) that can merge into larger irregular ulcers. Uncommon. More frequent in women and older adults. They heal in 1-2 weeks but tend to recur.

What Triggers Canker Sores

Nobody knows exactly what causes them. That's the frustrating truth. But researchers have identified a long list of triggers:

Mouth injury. Biting your cheek, scratching from braces or a sharp tooth, aggressive brushing, dental work. Probably the most common trigger. If you just got braces tightened in your orthodontist's office in Orem and a sore appeared the next day, that's no coincidence.

Stress. Finals week. Deadline at work. Tax season. Canker sores love stress. The immune system and stress are deeply linked, and canker sores appear to be an immune-mediated response.

Acidic and spicy foods. Tomatoes, citrus, pineapple, hot peppers, vinegar-based dressings. These don't cause canker sores, but they trigger outbreaks in people who are susceptible. They also make existing sores burn like fire.

Sodium lauryl sulfate (SLS). This is the foaming agent in most toothpastes. Multiple studies have shown that switching to an SLS-free toothpaste reduces canker sore frequency. If you get canker sores more than a few times a year, try this first. Brands like Sensodyne, Biotene, and Tom's of Maine (some formulas) skip SLS.

"A randomized controlled trial demonstrated a statistically significant reduction in aphthous ulcer occurrence when patients switched to SLS-free dentifrice." — Journal of the American Dental Association

Vitamin deficiencies. Low levels of B12, iron, and folate are associated with recurrent canker sores. A simple blood test can check these. If you're deficient, supplementing often reduces outbreaks dramatically.

Hormonal changes. Some women get canker sores tied to their menstrual cycle. Pregnancy can increase or decrease frequency — it varies.

Food sensitivities. Gluten, dairy, nuts, and chocolate are common culprits for some people. Not an allergy necessarily, but an immune response that manifests as mouth sores.

How to Treat a Canker Sore

Most minor canker sores heal in 7-14 days without any treatment. But "wait it out" is cold comfort when you can't eat lunch without wincing. Here's what actually helps speed healing and reduce pain:

Home Treatments

Saltwater rinse. Half a teaspoon of salt in 8 ounces of warm water. Swish for 30 seconds, 3-4 times a day. It stings for a second, then the area feels calmer. Salt draws out fluid from the sore, reduces bacteria, and promotes healing. Free and effective.

Baking soda paste. Mix baking soda with a few drops of water to make a paste. Apply directly to the sore. Neutralizes acids and creates an environment that's hostile to bacteria. Apply a few times daily.

Milk of magnesia. Dab a small amount directly on the sore with a cotton swab, 3-4 times a day. It coats the ulcer and neutralizes the acidic environment. Sounds weird. Works well.

Honey. Apply raw honey directly to the sore. Honey has natural antibacterial and anti-inflammatory properties. One study found honey reduced canker sore pain, size, and healing time better than some OTC treatments. Use raw/medical grade, not the squeeze bear.

OTC Products

Benzocaine gels (Orajel, Anbesol). Numb the sore so you can eat. Relief is immediate but temporary — 15-30 minutes. Reapply before meals.

Canker-Rid. Liquid herbal formula applied directly. Burns for 10 seconds, then provides hours of relief. Has a devoted following. Available at most Utah pharmacies and on Amazon.

Kanka. Forms a protective coating over the sore. Lasts longer than benzocaine gels because the film layer stays put. Stings on application.

DenTek Canker Cover patches. Stick-on patches that cover the sore and release medication over hours. Good for sores on the inner cheek or lip.

Prescription Treatments

For people who get canker sores frequently or get major/herpetiform types, your dentist or doctor can prescribe:

• Fluocinonide gel (Lidex) — a topical corticosteroid that reduces inflammation and speeds healing
• Amlexanox paste (Aphthasol) — specifically designed for canker sores, applied four times daily (note: availability varies, it's been harder to find in recent years)
• Dexamethasone rinse — a corticosteroid mouth rinse for multiple or hard-to-reach sores
• Debacterol — a chemical cauterizer applied by your dentist in-office, seals the sore in one visit

The Utah Dry Air Factor

If you live in Utah, your mouth dries out faster than people on the coasts. That matters for canker sores.

Dehydration reduces saliva production. Saliva is your mouth's natural defense system — it buffers acids, fights bacteria, and keeps tissues healthy. When your mouth is dry, canker sores take longer to heal and are more likely to develop in the first place.

Salt Lake City averages about 30% relative humidity in winter. Up in Park City or the Heber Valley, it's even drier. Add altitude (which increases water loss through breathing) and indoor heating, and your mouth is working in desert conditions.

What to do:

• Drink more water than you think you need. 8-10 glasses minimum, more if you're active or at higher elevation.
• Run a humidifier in your bedroom.
• If you mouth-breathe at night (and plenty of people do, especially at altitude), consider a bedside humidifier specifically for this.
• Avoid alcohol-based mouthwashes — they dry your mouth further. Biotene makes an alcohol-free version that actually helps.

Prevention: Reducing How Often You Get Canker Sores

You can't eliminate them completely. But you can significantly reduce frequency:

• Switch to SLS-free toothpaste. Try it for two months. Many people see a dramatic reduction in outbreaks.
• Identify your trigger foods and minimize them. Keep a food diary if you're getting sores frequently.
• Get your B12, iron, and folate levels checked. A standard blood panel at any Utah clinic will cover this. Supplement if deficient.
• Manage stress. Easier said than done. But if you notice sores always appear during high-stress periods, that's your signal.
• Protect your mouth from injury. If braces are causing sores, ask your orthodontist for dental wax. If a sharp tooth edge keeps cutting your cheek, get it smoothed.
• Don't skip dental cleanings. A healthy mouth environment reduces sore frequency.

When to See Your Utah Dentist About Mouth Sores

Most canker sores are nothing to worry about. See a dentist if:

• A sore lasts longer than 3 weeks without healing
• Sores are unusually large (bigger than a dime)
• Pain is so severe that you can't eat or drink enough
• You're getting sores more than once a month
• You have a high fever along with mouth sores
• Sores are spreading or getting worse instead of better
• You notice a sore that's hard, painless, or doesn't look like your usual canker sores

That last point is important. Oral cancer can look like a mouth sore that won't heal. This isn't meant to scare you — the vast majority of mouth sores are benign. But a sore that's been there for 3+ weeks, especially if it's painless, firm, or has irregular borders, needs to be examined. Your dentist can do a quick visual screening and determine if a biopsy is warranted.

"Any oral ulceration that persists for more than three weeks should be evaluated to rule out malignancy." — American Dental Association

Early detection of oral cancer has a dramatically better survival rate. A 5-minute screening at your regular dental checkup can catch it early.

Questions to Ask Your Utah Dentist

If you're dealing with frequent or severe canker sores, bring these questions to your next appointment:

1. Should I get bloodwork to check for vitamin deficiencies? (B12, iron, folate)
2. Could any of my medications be causing these? (Some blood pressure and arthritis meds increase canker sore risk)
3. Do you recommend any specific SLS-free toothpaste brands?
4. Is this sore something I should biopsy? (Ask if any sore has lasted 3+ weeks or looks different from your usual pattern)
5. Would a prescription topical help in my case?
6. How often should I be getting oral cancer screenings? (The ADA recommends screening at every dental visit)
7. Could this be related to another condition? (Celiac disease, Crohn's, and Behçet's disease all involve recurrent mouth sores)

If you have PEHP or SelectHealth insurance, routine dental exams that include oral cancer screening are typically covered under preventive care. Check your specific plan for details.

The University of Utah School of Dentistry also provides oral pathology evaluations if your general dentist refers you for a sore that needs further examination.

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Dealing with mouth sores that won't quit? Find a general dentist near you through our Utah provider directory. Regular dental care is the best way to catch problems early and keep your mouth healthy — from Ogden to Provo and everywhere in between.