Got canker sores? Try switching your toothpaste.

Experts caution that the studies are small and that more trials are needed to better understand how the ingredient may affect canker sores. But clinicians said switching to an SLS-free toothpaste has helped several patients.

“They’re able to brush their teeth without feeling a burning sensation,” said Alessandro Villa, the chief of oral medicine and oral oncology at Miami Cancer Institute.

Diana Messadi, a professor and the chair of oral medicine, oral pathology and orofacial pain at the UCLA School of Dentistry, said she suggests the switch to her patients because it’s harmless and the upside can be significant.

“Minor changes in a toothpaste can really make a difference in a patient’s quality of life,” Messadi said.

The link between toothpaste and canker sores

Canker sores are painful, round ulcers that form on the soft tissue in the mouth, such as the inside of the cheeks or lips.

The ulcers often start with a minor trauma to the mucosal lining, said Richard Wender, the chair of family medicine and community health at the Perelman School of Medicine at University of Pennsylvania. A sharp edge on a tooth or a pair of prickly braces could irritate the mouth. Or a person could be biting their cheeks.

One theory as to how SLS could then trigger a canker sore is that the ingredient could disrupt the protective layer of mucus covering the mucosa — the skin of the mouth, Villa said.

But there is no definitive explanation, said Vikki Noonan, a clinical professor and the director of the division of oral pathology at the Boston University Henry M. Goldman School of Dental Medicine.

Sook-Bin Woo, a professor of oral medicine and oral pathology at Harvard Medical School, said it is also possible that other ingredients in SLS toothpastes could be causing pain.

“I find a lot of the time it is the mint and all the strong additives in adult toothpaste that causes the symptoms,” Woo said.

Companies that sell toothpaste say SLS is a commonly used ingredient. A spokesperson for Crest, a Procter & Gamble brand, said in an email that “many toothpastes contain SLS because it is safe and effective at removing food debris from teeth.”

What toothpastes are free of SLS?

Toothpastes without sodium lauryl sulfate include Crest Pro-Health Densify Active Repair Toothpaste and Sensodyne’s Extra Whitening, Fresh Mint, Full Protection and Pronamel toothpastes.

To find out if your toothpaste contains SLS, check the ingredients on the label. Sometimes, the label on the tube lists only active ingredients, but the entire list can be found online.

Patients can also ask their health-care provider for recommendations, said Richard Vargo, an oral and maxillofacial pathologist at the University of Pittsburgh School of Dental Medicine.

Woo said she advises her patients to use children’s toothpastes because those consist of “very mild ingredients.”

What causes canker sores?

Experts say the exact cause of canker sores isn’t known, but it’s likely multifactoral, with different reasons for different people.

Stress, a family history of canker sores and certain nutritional deficiencies have all been associated with a higher risk of developing the ulcers. In some patients with a family history, “there is some type of defect in the immune system” that seems to be related to the inflammatory reaction in the mouth, said A. Ross Kerr, the director of oral medicine at New York University College of Dentistry.

A lack of vitamin B12, folic acid, iron or zinc has also been associated with development of the sores.

Acidic, citric or spicy foods can irritate existing ulcers and potentially worsen symptoms. But there’s not enough evidence to say that the acidity of these foods can trigger canker sores, Kerr said.

Canker sores, which occur inside the mouth, are not contagious or caused by a virus. They are different from cold sores, which are typically found on the outside of the lip and are contagious.

How can you get rid of canker sores?

Medical treatments: Medications can help mitigate pain and reduce inflammation. Over-the-counter anesthetics, such as benzocaine, can provide fast, temporary pain relief.

Topical steroids, such as clobetasol gel, and other prescription medications are used for larger ulcers or recurrent canker sores to reduce inflammation, Vargo said. There are also treatments, such as Debacterol, that chemically cauterize the wound.

Saltwater rinses: The salt might “slightly cauterize” the canker sore and reduce inflammatory cells, Wender said in an email. There are no clinical trials proving its benefit, but “we’ve used and recommended saltwater rinsing for years,” he said.

Wender recommends stirring half a teaspoon of salt into eight ounces of warm water until the salt completely dissolves. Swish for 15 to 30 seconds and spit it out. It’s fine to swish and rinse your mouth throughout the day, often three to four times a day, he said.

Supplements: Further research is needed to understand whether supplements can help treat canker sores, but some studies suggest that vitamin B12 might help. In a randomized controlled trial of 58 people with canker sores, patients were given 1,000 micrograms of vitamin B12 daily for six months. The study, which was partly funded by a pharmaceutical company, showed that the vitamin group experienced a significant reduction in the duration of the sores, the number of ulcers and the amount of pain compared with a control group.

Similar studies of zinc supplements have come to conflicting conclusions.

When to see a doctor

Talk to your doctor if you have three or more canker sores at a time, or when it seems you always have ulcers in your mouth or an ulcer that is getting progressively worse, experts say. These could be a sign of underlying medical conditions, such as Crohn’s or celiac disease, or an oral cancer.

“Having mouth sores is not abnormal,” said Ashley C. Mays, a head and neck oncology surgeon at Cleveland Clinic in Vero Beach, Fla. “It’s the ones that persist past a couple weeks, and are progressing, that warrant an evaluation.”