Most mouth ulcers heal on their own within one to two weeks, but you can speed that process and cut the pain significantly with the right combination of rinses, topical treatments, and dietary adjustments. The approach depends on the size and severity of the ulcer, how often you get them, and whether an underlying cause is driving recurrence.
What Type of Ulcer You’re Dealing With
Mouth ulcers (also called canker sores or aphthous ulcers) fall into three categories. Minor ulcers are the most common: small, shallow, less than 1 cm across, and they heal without scarring. Major ulcers are larger and deeper, and they’re more likely to leave a scar. Herpetiform ulcers appear as clusters of many small sores at once.
These are not the same as cold sores. Cold sores are caused by the herpes simplex virus and form on the outside of the mouth, usually around the border of the lips. Canker sores have no known viral cause and only form inside the mouth, on the inner cheeks, lips, or tongue. The treatments below apply to canker sores, not cold sores.
Salt Water and Baking Soda Rinses
The simplest and cheapest treatment is a rinse you can make at home. Mix 1 teaspoon of table salt and 1 teaspoon of baking soda into 4 cups of warm water. Swish it around your mouth for 30 seconds or so, then spit it out. You can repeat this every four to six hours. The salt helps draw fluid from the swollen tissue, and the baking soda creates a mildly alkaline environment that’s less irritating than acidic saliva.
This won’t make an ulcer vanish overnight, but it keeps the area clean, reduces bacterial buildup, and makes the sore less painful while your body heals it.
Over-the-Counter Gels and Rinses
If a rinse isn’t enough, pharmacy shelves have several options that form a protective coating over the ulcer or numb the pain directly. The key is to apply them early, ideally as soon as you notice the sore forming.
- Numbing gels and pastes containing benzocaine (sold under names like Anbesol and Zilactin-B) provide temporary pain relief by dulling the nerve endings at the surface. Apply a small amount directly to the ulcer before meals or whenever the pain flares.
- Antiseptic mouth rinses with hydrogen peroxide (such as Orajel Antiseptic Mouth Sore Rinse) help keep the ulcer clean and reduce the chance of a secondary bacterial infection slowing healing.
These products work best for minor ulcers. If you’re dealing with a large, deep sore or ulcers that keep coming back, you may need something stronger.
Prescription Treatments for Severe Ulcers
For major ulcers or frequent recurrences, a dentist or doctor can prescribe a steroid dental paste. The most common option contains a low concentration of a corticosteroid that reduces inflammation directly at the sore. You press a small amount onto the ulcer at bedtime so it stays in contact with the tissue overnight. For more severe cases, you may need to apply it two or three times a day, ideally after meals so food doesn’t wipe it away immediately.
Prescription-strength treatment is worth pursuing if your ulcers are large enough to interfere with eating or talking, take longer than two weeks to heal, or recur frequently throughout the year.
Foods That Make Ulcers Worse
What you eat while you have an ulcer can make a noticeable difference in how much it hurts and how quickly it heals. Acidic foods and drinks lower the pH inside your mouth, disrupting the protective layer over your tissue and leaving the ulcer more exposed. The obvious culprits are citrus fruits, fizzy drinks, and alcohol. Less obvious ones include strawberries and tomatoes, which are more acidic than most people realize.
Spicy and very salty foods irritate the delicate lining of the mouth directly. And texture matters too: anything hard, crunchy, or sharp (think crusty bread, chips, raw carrots) can physically scrape against the ulcer and reopen it. While you’re healing, softer foods at mild temperatures will keep you more comfortable and let the tissue repair without constant re-injury.
Nutritional Deficiencies That Cause Recurrence
If you get mouth ulcers repeatedly, the problem may not be local. It may be nutritional. Three deficiencies are most closely linked to recurrent ulcers: vitamin B12, folate, and vitamin C. Low B12 is defined as serum levels below 200 pg/mL, low folate as serum levels below 3 ng/mL, and low vitamin C as plasma levels below 0.2 mg/dL.
You don’t need to memorize those numbers. The practical takeaway is this: if you’re getting ulcers every few weeks or months, especially if you also feel unusually tired or notice tingling in your hands and feet, ask your doctor for a blood test to check these levels. Correcting the deficiency with supplements or dietary changes can break the cycle of recurrence in ways that no topical gel ever will. Foods rich in B12 (meat, fish, eggs, dairy), folate (leafy greens, legumes, fortified grains), and vitamin C (peppers, broccoli, citrus when you don’t have an active sore) are worth prioritizing.
SLS-Free Toothpaste: Does It Help?
You may have seen advice to switch to a toothpaste free of sodium lauryl sulfate, the foaming agent in most toothpastes. The theory is that SLS irritates the mouth lining and triggers ulcers. The evidence, however, is thin. A 2019 review found there wasn’t enough data to confirm that SLS-free toothpastes reduced ulcer frequency, duration, pain, or number. One well-designed study found no significant change in ulcer patterns after switching.
That said, SLS-free toothpastes aren’t expensive and some people do report subjective improvement. It’s a low-risk experiment if you’re looking for anything that might help, but don’t expect dramatic results.
When an Ulcer Needs Medical Attention
Most mouth ulcers are harmless and temporary. But an ulcer that hasn’t healed after three weeks is a different situation. Guidelines in the UK recommend urgent specialist referral for any unexplained mouth ulcer lasting three weeks or more, because a non-healing ulcer can occasionally be a sign of oral cancer. The same applies if you notice an unexplained lump in your neck, hardening or thickening of tissue inside your mouth, or an ulcer that keeps growing rather than shrinking.
Other reasons to get a professional evaluation: ulcers accompanied by high fever, ulcers so large or painful you can’t eat or drink enough fluids, or more than three or four outbreaks per year with no obvious trigger. A doctor can check for underlying conditions like celiac disease, inflammatory bowel disease, or immune system issues that sometimes show up as persistent oral ulcers first.