Most canker sores heal on their own within a few weeks, but you can significantly reduce pain and speed things along with the right approach. The key is starting treatment early, keeping the sore clean, and avoiding anything that irritates it further.
Make Sure It’s Actually a Canker Sore
Canker sores appear inside your mouth, typically on the inner cheeks, tongue, soft palate, or base of the gums. They look like a single round white or yellow sore with a red border. They are not contagious.
Cold sores (fever blisters) are a different thing entirely. They show up on the outside of the mouth around the lips, appear as clusters of small fluid-filled blisters, and are contagious. If your sore is outside your mouth or looks like a blister, you’re dealing with a cold sore and need a different treatment plan.
How Long Canker Sores Last
Minor canker sores, the most common type, are smaller than a pea (under one centimeter across). These typically heal within a few weeks without leaving a scar. The pain is usually worst in the first three to four days, then gradually fades.
Major canker sores are larger than one centimeter, extremely painful, and can take months to heal. They often leave scars. If your sore is unusually large or deep, it falls into this category and may need professional treatment.
Home Remedies That Actually Help
A saltwater rinse is the simplest and most reliable first step. Mix one teaspoon of salt into eight ounces of warm water and swish gently for 30 seconds, then spit. If the sting is too much, cut the salt to half a teaspoon for the first day or two. Repeat several times a day, especially after meals. The salt draws fluid from the sore, reduces bacteria, and promotes healing.
Applying a small amount of milk of magnesia directly to the sore with a cotton swab can coat and soothe it. Holding a small ice chip against the sore also provides temporary pain relief by numbing the area. Avoiding acidic, spicy, or rough-textured foods while the sore is active makes a noticeable difference in daily comfort.
Over-the-Counter Pain Relief
Topical numbing gels and ointments containing benzocaine are widely available and can take the edge off quickly. Apply the gel, spray, or ointment directly to the sore up to four times a day. Don’t use benzocaine products for more than two consecutive days without checking with a doctor, and avoid using them on children under two due to toxicity risk.
You can also find over-the-counter protective pastes that form a barrier over the sore, shielding it from food, drinks, and your teeth. These work best when applied after drying the area with a tissue so the paste sticks. Look for products specifically labeled for mouth sores at any pharmacy.
When a Dentist or Doctor Can Help
For sores that won’t respond to home care, a dentist can chemically cauterize the ulcer. One common option uses a topical solution that chemically seals the sore’s surface and can reduce healing time to about a week for serious ulcers. Silver nitrate is another chemical cauterization option. It may not speed healing, but it typically provides significant pain relief by destroying the exposed nerve endings on the sore’s surface.
For severe or frequently recurring canker sores, a doctor may prescribe a steroid mouthwash. The typical protocol involves swishing (not swallowing) a small amount of the solution for five minutes, three times a day, then avoiding food and drink for 15 minutes afterward. These prescription rinses reduce inflammation and can shorten flare-ups considerably.
Preventing Canker Sores From Coming Back
If you get canker sores repeatedly, the cause is often something you can identify and change. Common triggers include biting your cheek, brushing too aggressively, sodium lauryl sulfate in toothpaste (switching to an SLS-free brand helps many people), hormonal shifts, stress, and food sensitivities to things like citrus, chocolate, or nuts.
Nutritional deficiencies play a role more often than people realize. Low levels of iron, folate, and vitamin B12 are all linked to recurrent canker sores. A clinical trial tested 1,000 micrograms of sublingual vitamin B12 daily and found it reduced outbreaks in people with recurring sores. If you get canker sores frequently, it’s worth asking your doctor to check your levels of these nutrients.
Signs a Canker Sore Needs Medical Attention
Most canker sores are annoying but harmless. Seek medical evaluation if you notice any of the following:
- A sore lasting longer than two weeks
- Recurring sores where new ones develop before old ones heal
- Unusually large sores
- Sores extending onto the outer lip border
- Pain severe enough that you can’t eat or drink
- High fever accompanying the sores
Persistent or unusually frequent canker sores can occasionally signal an underlying condition like celiac disease, an immune disorder, or a nutritional deficiency that needs treatment beyond what topical remedies can offer.