Most mouth ulcers heal on their own within one to two weeks, and the best thing you can do is manage pain, protect the sore from further irritation, and avoid triggers that slow healing. If an ulcer sticks around for more than three weeks, that’s the point where you need professional evaluation. In the meantime, there’s a lot you can do at home to speed things along.
Saltwater Rinses: The Simplest First Step
A warm saltwater rinse is the most accessible and effective starting point. Dissolve half a teaspoon of table salt in a glass of lukewarm water and swish gently for 30 seconds before spitting it out. This draws fluid away from the swollen tissue, temporarily reducing inflammation and creating a less hospitable environment for bacteria. You can do this several times a day, especially after meals when food particles are most likely to irritate the sore.
Over-the-Counter Pain Relief
Numbing gels and liquids containing benzocaine can take the edge off, particularly before eating. Apply a small amount directly to the ulcer up to four times a day, and don’t use it for more than two days without checking with a doctor or pharmacist. Benzocaine carries a small risk of a blood condition called methemoglobinemia, which is rare but more of a concern in young children under two.
Dabbing a small amount of milk of magnesia directly onto the ulcer a few times a day creates a protective coating that shields the sore from contact with food and saliva. This approach works well on its own or alongside a numbing gel.
Protecting the Ulcer From Irritation
Many ulcers are caused or worsened by mechanical irritation: a sharp tooth edge, a rough bracket on braces, or even aggressive brushing. If braces are the culprit, orthodontic wax pressed directly over the bracket near the problem area creates a smooth barrier. The wax breaks down over time and needs reapplying, but it’s non-toxic and safe to accidentally swallow. It’s available at most pharmacies and small enough to carry with you.
If a chipped tooth or rough filling is catching the inside of your cheek or lip, a dental visit to smooth it down can prevent ulcers from recurring in the same spot. In the meantime, use a soft-bristled toothbrush and brush gently around the area.
Foods and Drinks to Avoid
Acidic foods like citrus fruits, tomatoes, and vinegar-based dressings will sting on contact and can delay healing. Spicy food, very salty snacks, and crunchy items like chips or toast are also common irritants. Stick to softer, cooler, and blander foods while the ulcer is active. Drinking through a straw can help liquids bypass the sore.
You may have heard that switching to a toothpaste without sodium lauryl sulfate (SLS, the foaming agent in most toothpastes) can reduce ulcer recurrence. The evidence on this is mixed. A 2019 review found there wasn’t enough data to confirm that SLS-free toothpastes reduce ulcer frequency, duration, or pain. It’s worth trying if you get ulcers frequently, since SLS-free options are easy to find, but don’t expect a guaranteed fix.
When Prescription Treatment Helps
For larger or especially painful ulcers that aren’t responding to home care, a prescription steroid paste can make a real difference. These pastes work by reducing inflammation directly at the site. The paste is applied after meals and at bedtime using a cotton swab, pressed gently onto the ulcer to form a thin film. Don’t rub it in, as the paste becomes gritty and won’t adhere properly. This protective film reduces pain and gives the tissue underneath a better chance to heal.
Nutritional Gaps That Cause Recurring Ulcers
If you’re getting mouth ulcers repeatedly, the problem may not be local at all. Deficiencies in vitamin B12, folate, and iron are well-established causes of recurring oral ulcers. B12 and folate deficiency can also cause a sore, reddened tongue alongside the ulcers. These deficiencies are common in people with restrictive diets, heavy menstrual periods, or digestive conditions that reduce nutrient absorption. A simple blood test can identify them, and supplementation often resolves the ulcer pattern entirely.
Mouth Ulcers vs. Cold Sores
It’s easy to confuse the two, but they’re completely different. Mouth ulcers (canker sores) appear inside the mouth, typically as a single round sore with a white or yellow center and a red border. Their cause is unknown. Cold sores (fever blisters) show up on the outside of the mouth, around the lips, as clusters of small fluid-filled blisters. Cold sores are caused by herpes simplex virus type 1 and are contagious, while mouth ulcers are not.
This distinction matters because the treatments are different. Antiviral medications work on cold sores but do nothing for canker sores, and the protective coatings and steroid pastes used for canker sores aren’t appropriate for viral blisters.
Signs an Ulcer Needs Professional Attention
The three-week mark is the key threshold. Any mouth ulcer that hasn’t healed after three weeks warrants a visit to your doctor or dentist. Other reasons to seek care sooner include ulcers that are unusually large (bigger than a pencil eraser), ulcers that keep coming back in clusters, sores accompanied by a high fever, or pain so severe that you can’t eat or drink enough to stay hydrated. Persistent ulcers that don’t heal can occasionally signal other conditions that need investigation, including in rare cases oral cancer, which is why the three-week guideline exists.