Most canker sores heal on their own within 10 to 14 days, but a bad one can make eating, drinking, and talking miserable in the meantime. The fastest way to get relief is to start treating it as soon as you notice the telltale tingling or spot forming. A combination of topical pain relief, gentle mouth rinses, and avoiding irritating foods can significantly cut down on discomfort and may speed healing.
What Makes a Canker Sore “Bad”
Canker sores come in different sizes. Minor ones, the most common type, are small round or oval ulcers with a white or yellow center and a red border. They show up inside the mouth on the cheeks, lips, tongue, or soft palate, and they typically resolve in 10 to 14 days without scarring.
Major canker sores are a different experience. They’re larger, deeper, and intensely painful. These can take up to six weeks to heal and sometimes leave scars. If you’re searching for how to get rid of a “bad” canker sore, you may be dealing with one of these larger ulcers, or a minor one that landed in a particularly painful spot like the tongue or the inside of the lip where it rubs against your teeth constantly.
Over-the-Counter Products That Work
The most effective OTC approach is a topical numbing gel or paste applied directly to the sore. Look for products containing benzocaine (sold as Anbesol, Orabase, or Zilactin-B), which temporarily blocks pain signals from the nerve endings in the ulcer. Apply these right before meals to make eating less painful, and reapply as directed on the label.
Hydrogen peroxide rinses (like Orajel Antiseptic Mouth Sore Rinse) serve a different purpose. They help keep the area clean and reduce bacteria around the ulcer, which supports faster healing. You can also find combination products that both numb and protect the sore by forming a temporary barrier over it.
The key with any topical product is timing. Applying it at the first sign of a sore, when you feel that initial burning or tingling sensation, gives you the best chance of reducing its severity.
Home Rinses Worth Trying
A simple saltwater or baking soda rinse is one of the oldest and most reliable home treatments. Memorial Sloan Kettering Cancer Center recommends mixing 1 teaspoon of salt and 1 teaspoon of baking soda into 1 quart (4 cups) of water. You can also use just salt or just baking soda in the same ratio. Swish gently for 30 seconds and spit. Repeat every four to six hours.
The salt draws fluid out of the inflamed tissue, which can reduce swelling. Baking soda shifts the pH in your mouth to a more alkaline environment, making it less hospitable to bacteria. Neither will sting the way pure salt on a wound might, because the solution is diluted enough to be gentle. Avoid commercial mouthwashes that contain alcohol, as these will burn and can further irritate the ulcer.
When to Ask Your Doctor or Dentist
If a canker sore hasn’t started improving after two weeks, or if you get them frequently, a prescription-strength treatment may help. Dentists and doctors can prescribe topical steroid gels like fluocinonide, which reduce the immune-driven inflammation that’s actually causing the ulcer. Your immune system’s T cells attack the lining of your mouth during a canker sore outbreak, and a topical steroid calms that response directly at the site.
Some dental offices also offer low-level laser treatment for canker sores. The procedure takes under a minute per session and can provide near-immediate pain relief while promoting faster tissue repair. It’s painless and considered safe regardless of age.
Foods and Habits That Make It Worse
While your sore is active, avoid anything acidic (citrus, tomatoes, vinegar-based dressings), spicy, or sharp-edged (chips, crackers, crusty bread). These don’t just hurt. They physically irritate the exposed tissue and can delay healing. Stick to soft, cool, bland foods. Smoothies, yogurt, mashed potatoes, and oatmeal are all good options.
Common triggers for developing canker sores in the first place include mouth injuries (biting your cheek, aggressive brushing, dental work), emotional stress, and certain food sensitivities. Some people find that switching to a toothpaste without sodium lauryl sulfate, a foaming agent that can irritate oral tissue, reduces how often they get sores.
Nutritional Deficiencies That Fuel Recurrence
If you get canker sores repeatedly, a nutritional gap may be involved. Deficiencies in vitamin B12, iron, zinc, and folic acid are all linked to recurrent outbreaks. This is worth exploring with your doctor through a simple blood test, especially if your sores keep coming back despite good oral hygiene and avoiding known triggers.
Some people also report that supplementing with L-lysine, an amino acid, helps shorten the duration of their sores. The evidence for this is largely anecdotal, but lysine is inexpensive and generally well tolerated. A typical dose people use is 1,000 mg daily during an active outbreak.
Canker Sore vs. Cold Sore
These two get confused constantly, but they’re completely different conditions. The easiest way to tell them apart is location. Canker sores appear inside the mouth. Cold sores (fever blisters) appear outside the mouth, usually on or around the lips. Cold sores are caused by the herpes simplex virus and are contagious. Canker sores are not caused by a virus and cannot be spread to another person.
Canker sores also look different. They’re typically a single round ulcer with a white or yellow center, while cold sores appear as clusters of small fluid-filled blisters that eventually crust over. If your sore is inside your mouth and isn’t a blister, it’s almost certainly a canker sore.
Signs a Sore Needs Professional Attention
Any mouth ulcer that hasn’t healed within two to three weeks should be evaluated by a dentist or doctor. The Oral Cancer Foundation notes that a nonhealing ulcer is one of the early signs of oral cancer, along with persistent red or white patches, progressive swelling, unusual bleeding, or sudden unexplained tooth looseness. A sore that doesn’t respond to normal treatment within that two to three week window should be biopsied to rule out something more serious.
Other reasons to seek care sooner: a canker sore larger than about half an inch across, sores that come with a high fever, difficulty swallowing or drinking enough fluids, or outbreaks that happen so frequently that one sore hasn’t healed before the next one appears.