Most mouth ulcers heal on their own within 1 to 2 weeks without any treatment. The exact timeline depends on the type and size of the ulcer, but the small, round sores that most people get (called canker sores or minor aphthous ulcers) are the most common and the quickest to resolve. Larger or deeper ulcers can take significantly longer.
Healing Times by Ulcer Type
There are three types of canker sores, and they follow very different timelines.
Minor ulcers are the kind most people experience. They’re usually less than 10 mm across, appear on the inner cheeks, lips, or tongue, and heal within 7 to 14 days without leaving a scar. About 80% of all canker sores fall into this category.
Major ulcers are deeper, larger, and considerably more painful. These can take up to 6 weeks to heal and often leave a scar. They tend to be bigger than 10 mm and may appear one or two at a time rather than in clusters.
Herpetiform ulcers are the least common type. Despite the name, they aren’t caused by the herpes virus. They show up as clusters of tiny, pinpoint sores that can merge into larger irregular ulcers. These generally heal within a few weeks, though the clusters can recur frequently.
When a Mouth Ulcer Isn’t a Canker Sore
Not every sore in or around your mouth is a canker sore, and the healing timeline varies depending on the cause.
Cold sores (fever blisters) appear outside the mouth, typically around the border of the lips, and are caused by the herpes simplex virus. Canker sores occur inside the mouth. Both tend to resolve on their own, but cold sores are contagious while canker sores are not.
In children, hand, foot, and mouth disease causes yellow-grey ulcers with red edges on the tongue and inside the mouth. These develop within a day or two of infection and typically pass within a week, though they can make eating and drinking painful in the meantime.
Mouth ulcers can also result from accidental bites, sharp food, braces, or ill-fitting dentures. These trauma-related sores usually heal within a week once the source of irritation is removed.
The 2-Week Rule Worth Knowing
A mouth ulcer that hasn’t started healing after 2 weeks deserves attention. Clinicians use 14 days as a key threshold: sores caused by infection, inflammation, or local trauma typically resolve within that window. If an ulcer persists beyond 2 weeks after any obvious irritant has been removed, a biopsy is strongly recommended to rule out oral cancer or other serious conditions. This doesn’t mean every lingering ulcer is dangerous, but it’s the point at which further investigation becomes important.
Other signs that warrant a closer look include ulcers that keep coming back in the same spot, sores that are unusually large or spreading, ulcers accompanied by unexplained weight loss or fever, or any lump or thickening near the ulcer.
What Speeds Up Healing
Most minor ulcers don’t need treatment, but several options can reduce pain and shorten healing time. Antimicrobial mouthwashes reduce bacterial buildup on the ulcer surface and calm local inflammation. In clinical testing, a 0.2% chlorhexidine rinse brought average healing time down to about 5 days, though higher concentrations can irritate the surrounding tissue. Over-the-counter versions at lower concentrations work more slowly but with fewer side effects.
Topical gels that form a protective barrier over the ulcer can reduce pain from eating and drinking. Prescription-strength anti-inflammatory pastes applied directly to the sore may help with major ulcers that are slow to heal. Avoiding spicy, acidic, or crunchy foods during healing makes a noticeable difference in day-to-day comfort.
Saltwater rinses (half a teaspoon of salt in a glass of warm water) are a simple home remedy that helps keep the area clean without irritating it further.
Why Some People Get Ulcers Repeatedly
If you’re dealing with mouth ulcers that keep returning, the cause is often hard to pin down. Stress, hormonal changes, and minor mouth injuries are common triggers. Some people notice flare-ups after eating certain foods, particularly citrus fruits, tomatoes, or chocolate.
Nutritional deficiencies play a role in some cases. Studies have found that deficiencies in vitamin B12, folic acid, or iron show up in 18 to 28 percent of people with recurrent canker sores, compared with about 8 percent of healthy controls. That said, one study of 90 patients with recurrent ulcers found only 3 had measurable deficiencies, so this isn’t the explanation for most people. If your ulcers keep coming back, it’s reasonable to have your levels checked, but supplementation only helps if you’re actually deficient.
Underlying conditions like celiac disease, inflammatory bowel disease, and immune system disorders can also cause frequent mouth ulcers. People with weakened immune systems, including those with HIV, may experience ulcers with extremely prolonged healing times, sometimes lasting months.
What to Expect Day by Day
A typical minor ulcer follows a predictable pattern. In the first day or two, you may feel a tingling or burning sensation before the sore becomes visible. The ulcer then forms as a shallow, round or oval crater, usually white or yellowish with a red border. Pain peaks in the first 3 to 4 days, which is when eating, drinking, and talking feel worst. By days 5 through 7, the pain starts fading, and the ulcer begins shrinking from the edges inward. Most are fully healed by day 10 to 14, with no trace left behind.
If your ulcer is following this trajectory, it’s behaving normally. If the pain is intensifying rather than fading after the first week, or the sore is growing instead of shrinking, that’s a sign something else may be going on.