Most canker sores heal on their own within one to three weeks, but you can reduce pain and speed things along with a few simple treatments. The key is keeping the sore clean, minimizing irritation, and using a topical product to manage discomfort while your body does the repair work.
What a Canker Sore Actually Is
A canker sore is a small, shallow ulcer that forms inside your mouth, on your tongue, the floor of your mouth, or the soft tissue of your cheeks and gums. It typically appears as a round white or yellow sore with a red border. The cause isn’t fully understood, but the immune system plays a central role. People with canker sores tend to have elevated levels of inflammatory signaling molecules in their blood compared to people who don’t get them, suggesting the ulcers are tied to an overactive immune response rather than an infection you can catch.
This is worth emphasizing: canker sores are not cold sores. Cold sores are caused by the herpes simplex virus, appear as fluid-filled blisters on the outside of your lips, and are contagious. Canker sores form inside the mouth, aren’t contagious, and aren’t caused by a virus you can pass to someone else.
Home Treatments That Help
A salt water or baking soda rinse is the simplest first step. Dissolve one teaspoon of baking soda in half a cup of warm water and swish it around your mouth several times a day. This creates an alkaline environment that reduces irritation and helps keep the area clean. A plain salt water rinse works similarly. Neither will make the sore vanish overnight, but both can ease the sting and support faster healing.
Over-the-counter topical gels and pastes containing a numbing agent (like benzocaine) can temporarily block pain. Apply them directly to the sore before meals to make eating less miserable. Some products also form a protective barrier over the ulcer, shielding it from food and saliva. Look for oral pain relief gels in the dental care aisle.
Honey has shown some promise as a natural option. In a small study comparing honey applied three times daily to a standard prescription gel, both groups saw similar improvements in pain and ulcer size over five days, with no significant difference between them. No side effects were reported in the honey group. It’s not a magic cure, but dabbing a small amount of honey on the sore a few times a day is a reasonable low-risk approach.
What to Avoid While You Heal
Acidic and spicy foods are the biggest day-to-day aggravators. Tomatoes, citrus fruits, vinegar-based dressings, hot peppers, and salty chips can all intensify the pain and slow healing. Stick to softer, blander foods until the sore closes up. Drinking through a straw can help keep acidic beverages away from the ulcer.
Try not to poke at the sore with your tongue or teeth. It’s tempting, but repeated irritation extends the healing timeline. If a sharp tooth edge or dental appliance is rubbing against the sore, that’s worth mentioning to your dentist, since the constant friction can trigger new sores or prevent current ones from healing.
How Long Healing Takes
The timeline depends on the type of canker sore you’re dealing with. Most people get minor canker sores, which are smaller than a pea (under one centimeter across). These typically heal within a few weeks and don’t leave scars.
Major canker sores are larger than one centimeter, significantly more painful, and can take months to heal. They often leave scars behind. Herpetiform canker sores are rare and look different: instead of one ulcer, you’ll see a cluster of tiny pinpoint sores grouped together. These usually heal within about two weeks without scarring.
Preventing Recurrences
If you get canker sores frequently, pay attention to patterns. Common triggers include stress, hormonal changes, minor mouth injuries (like biting your cheek or brushing too aggressively), and certain foods. Keeping a simple log of what you ate and how stressed you were in the days before an outbreak can help you identify your personal triggers.
You may have heard that switching to a toothpaste free of sodium lauryl sulfate (the foaming agent in most toothpastes) can reduce outbreaks. The evidence on this is mixed. A double-blind study found no significant change in ulcer frequency, duration, or pain when participants switched to SLS-free toothpaste, and a 2019 review concluded there wasn’t enough data to confirm a benefit. That said, some people do report improvement, and SLS-free toothpaste has no downside, so it’s worth trying if you get frequent sores.
Nutritional deficiencies in iron, zinc, folate, or B vitamins have also been linked to recurrent canker sores. If your outbreaks are frequent, a simple blood test can check whether a deficiency might be contributing.
When a Canker Sore Needs Medical Attention
Most canker sores don’t require a doctor’s visit, but certain situations call for one. Seek professional evaluation if you have sores lasting longer than two weeks, unusually large sores, recurring outbreaks where new sores develop before old ones heal, pain you can’t manage with over-the-counter treatments, extreme difficulty eating or drinking, sores extending onto the outer lip border, or a high fever accompanying the sores. In these cases, a doctor or dentist may prescribe a stronger topical treatment or investigate underlying causes like an autoimmune condition or nutritional deficiency.