Most canker sores heal on their own within 7 to 14 days. Canker sores typically heal within about two weeks, even without treatment (Cleveland Clinic). But "most" and "on their own" are doing a lot of work in that sentence. The actual duration depends on the type of canker sore, what triggered it, and whether you treat it.
| Stage | Timeframe | What happens |
|---|---|---|
| 1. Formation (prodrome) | Days 1–2 | Tingling, burning, or roughness in one spot; a small red spot appears and opens into an ulcer with a white/yellow centre and red border. |
| 2. Peak pain | Days 2–4 | The ulcer is fully open and nerve endings are exposed. Pain is at its worst; acidic and spicy foods sting the most. |
| 3. Gradual improvement | Days 4–7 | Healing begins. The ulcer looks slightly smaller, the red border fades, and eating becomes less painful. |
| 4. Resolution | Days 7–14 | The ulcer closes from the edges inward. By day 10–14 most minor canker sores are fully healed with no trace left behind. |
That timeline covers the typical minor canker sore. Below is a detailed breakdown of how healing time changes by type, what can slow it down, and when a sore that won't heal becomes a reason to see a professional.
How Long Do Canker Sores Last by Type?
Not all canker sores are the same. There are three types, and they heal at very different rates. About 80% of canker sores are minor and resolve within 7 to 14 days without scarring (StatPearls). Major and herpetiform sores follow their own timelines.
| Type | Share of cases | Healing time (untreated) | Scarring |
|---|---|---|---|
| Minor | ~80% | 7–14 days | No |
| Major | ~10% | Several weeks to months | Often — deeper tissue damage can scar permanently |
| Herpetiform | ~1–10% | 1–2 weeks | Sometimes — if clusters merge |
Minor Canker Sores (About 80% of Cases)
These are the most common canker sores — small, oval, shallow ulcers under 1 cm across, with a white or yellow centre and a red border. They heal in 7 to 14 days without treatment and don't scar (StatPearls). Pain is moderate: uncomfortable while eating and speaking, but manageable for most people.
Major Canker Sores (About 10% of Cases)
Major canker sores are larger than 1 cm, deeper, and considerably more painful. Untreated, they can take several weeks to months to resolve. Because the ulcer reaches deeper tissue, healing often leaves permanent scarring (StatPearls).
They may require medical attention, and over-the-counter treatments alone may not be sufficient. If you have a sore larger than 1 cm that isn't improving after 2 weeks, see your doctor.
Herpetiform Canker Sores (About 1–10% of Cases)
Herpetiform sores are very small — 1 to 2 mm each — but appear in clusters of 10 to 100 that can merge into larger, irregular ulcers. They usually heal within 1 to 2 weeks, though merged clusters sometimes scar. Estimates of how common they are vary, from about 1% to 10% of cases.
Despite the name, herpetiform canker sores are not related to the herpes virus. They get this name because the cluster pattern resembles herpes sores. They're more common in women and older adults.
What Affects How Long a Canker Sore Lasts?
Several factors influence healing speed:
Location
Canker sores on the tongue tend to take longer to heal because the tongue is constantly moving and in contact with food and teeth. Sores on the inner cheek or gum may heal slightly faster since they experience less friction.
Size and Depth
Larger and deeper sores take longer. A 2 mm sore may heal in a week; a major canker sore over 1 cm can persist for weeks or months.
Re-Injury
If you keep irritating the canker sore — biting it accidentally, brushing over it aggressively, eating rough foods — healing resets. This is one of the most common reasons canker sores last longer than expected.
Nutritional Status
Deficiencies in vitamin B12, iron, folate, and zinc are linked to slower wound healing. If you get frequent, slow-healing canker sores, nutritional factors may be involved. Read more in our guide on canker sores and diet.
Immune Health
Your immune system drives wound healing. Illness, chronic stress, poor sleep, and immune-suppressing medications can all slow the process.
Treatment
This is the factor you can control most directly. Untreated canker sores follow the 7–14 day timeline. Treated canker sores can heal faster depending on the method used.
Can You Make a Canker Sore Heal Faster?
Yes. Treatment reduces both pain duration and total healing time.
The key difference: benzocaine gels manage pain but don't change healing speed. Treatments that address the ulcer itself — like chemical cautery or corticosteroids — can shorten the total cycle.
ORALMEDIC is a single-application treatment that seals the canker sore behind a protective barrier — and according to the manufacturer, supports healing within 3 to 5 days, compared with the roughly two-week course of an untreated minor sore.
For a full breakdown of all treatment options, read how to get rid of a canker sore fast.
When a Canker Sore Lasts Too Long — Warning Signs
See your doctor or dentist if:
- The sore hasn't healed after 2 weeks — minor canker sores should resolve by then. Persistence may indicate a major canker sore or another condition.
- It's getting larger, not smaller — canker sores should gradually shrink after the first week.
- The pain is worsening, not improving — pain should peak around days 2–4 and then gradually decrease.
- You develop fever, fatigue, or swollen lymph nodes — these may indicate a secondary infection or systemic condition.
- You get 3 or more outbreaks per month — frequent recurrence may point to an underlying issue like nutritional deficiency, celiac disease, or an immune condition. Learn more about recurring triggers in what causes canker sores.
- The sore appears unusual, or still hasn't healed after 3 weeks — an irregular shape, hard or raised borders, or white/red patches that don't look like a typical canker sore warrant professional evaluation. Any mouth ulcer that does not heal should be assessed by a doctor or dentist to rule out other conditions, including oral cancer.
A healthcare provider can rule out other conditions, check for nutritional deficiencies, and prescribe stronger treatments if needed.
Frequently Asked Questions
How long do canker sores last?
Most canker sores are minor and heal on their own within 7 to 14 days. Major canker sores are larger and can take several weeks to months, and may leave a scar. Herpetiform sores usually clear within one to two weeks. How long a sore lasts depends on its type, size, location, and whether it is treated.
What are the stages of a canker sore?
A canker sore moves through four stages. Formation on days 1 to 2 brings tingling, then an open ulcer with a white centre and red border. Peak pain hits on days 2 to 4. Gradual improvement follows on days 4 to 7 as the border fades, and resolution is usually complete by days 7 to 14.
How long do major canker sores take to heal?
Major canker sores are larger and deeper than minor ones, so they take longer to resolve, often several weeks or more. Because they reach deeper tissue, they can leave permanent scarring. If a canker sore has not healed after two weeks, see a doctor or dentist to rule out other conditions.
Can you make a canker sore heal faster?
Yes. Benzocaine gels ease pain but do not speed healing. Treatments that act on the ulcer itself, such as chemical cautery or corticosteroids, can shorten the cycle. Starting treatment early makes the biggest difference, because the sooner you treat a canker sore, the shorter its overall course tends to be.
When should you see a doctor about a canker sore?
See a doctor or dentist if a canker sore has not healed after two weeks, keeps getting larger, becomes more painful instead of less, or looks unusual with hard or irregular borders. Also seek care if you develop fever, fatigue, or swollen lymph nodes, or get three or more outbreaks per month.
The Bottom Line
Most canker sores are minor and heal within about two weeks on their own. But if you're in pain now and want faster relief, early treatment makes a measurable difference. The sooner you treat it, the shorter the cycle.
Have questions? Visit our FAQ or contact us.
This article is for general information only and is not a substitute for professional dental or medical advice. If a mouth ulcer lasts longer than three weeks, is unusually large or painful, or keeps recurring, see a dentist or physician. ORALMEDIC is a Class I medical device; always follow the product instructions.