If you’re chronic canker sore sufferer, we don’t need to tell you how painful these nasty mouth ulcers are. And if you get them so infrequently that you’re not sure why we would even create this story, consider yourself lucky. (See the use of adjectives “painful” and “nasty” above.)

Lots of people confuse canker sores with cold sores, but there’s a big difference: Cold sores are contagious, while canker sores aren’t.

Plus, canker sores form within your mouth, especially on the inside of your lips and inner cheek walls, said Dr. Shilpi Agarwal, a board-certified family medicine physician at One Medical Group in Washington, D.C. They also pop up on your tongue and gums.

Another distinction is that we know what causes cold sores: the herpes virus. (See How to Get Rid of a Cold Sore Faster.)

But the root of canker sores is tougher to pin down. Some experts believe they’re caused by a weakened immune system, high levels of stress, or a lack of certain nutrients—such as iron and vitamin B. However, no one knows for sure.

And that’s what makes canker sores so frustrating to people who are particularly prone to them. After all, no known cause usually means no known cure.

The good news is that, in terms of your health, you don’t really have to worry about cankers unless you also experience symptoms like fatigue or bowel problems at the same time. These could be indicative of digestive disorders and autoimmune diseases like celiac disease and inflammatory bowel disease. (Signs you should consult a doctor.)

Some foods seems to trigger canker sores, including chocolate and spicy, salty, and acidic items. These foods can also make canker sores feel worse. Using mouthwashes or toothpastes with the ingredient sodium lauryl sulfate may also spur a reaction.  

In most cases, canker sores only tend to stick around for a week or two. But if you have one that hangs around for longer, seek help.

“Any sore in the mouth that does not heal should be checked for oral cancer,” said Dr. David Edelberg, an internist at WholeHealth Chicago.

For temporary relief, try an over-the-counter oral pain relief gel like Orajel, which contains the mild anesthetic benzocaine, advised Agarwal. But if the sores cause you severe pain, your doctor may prescribe a special mouthwash that contains dexamethasone, which relieves pain and inflammation. You can also use salt water or baking soda to numb the canker sore, Edelberg said.

This is all based on what’s known medically, and is probably a little depressing if these mouth sores regularly plague you. But there may be an anecdotal antidote worth trying.

“I found that 2,000 milligrams of lysine, taken every day, has eliminated my canker sores,” said Adam Campbell, editor of MensHealth.com, who reports that until he adopted the regimen two years ago, he had experienced canker sores frequently since childhood.

“It could also be a coincidence: Maybe I have just ‘grown out of them,’ if that’s possible. And to be clear, this is in no way medical advice. But I wanted to at least share my personal finding so that others could consult about it with their family physician.”

For the record, based on the available evidence, no doctor or researcher felt comfortable suggesting that lysine supplementation could be helpful in the prevention of canker sores.

But Men’s Health nutrition advisor Mike Roussell, Ph.D. does say that taking 2,000 milligrams (mg) per day of lysine—which is an amino acid that’s found in every day foods—would be considered a safe dose.

The idea to use lysine came from research that suggests that it may help reduce the outbreaks of cold sores.

“I realize they’re different, but I tried it anyway given that it appears to be safe and that other preventative measures haven’t worked for me,” Campbell said.

“I seem far more prone to cankers sores when I’m really stressed or sick, so I’m extra vigilant about lysine supplementation at those times. And for me, it appears to be effective.”

Be smart: Before starting any supplement regiment, have a discussion with your doctor to ensure that you don’t have any conditions or medications that might be negatively impacted.