Here’s Why You Keep Getting Canker Sores

Photographed by Erin Yamagata.
Canker sores are like cold sores' obnoxious siblings: They're both annoying, painful, and seem to pop up out of nowhere. Plus, your whole family probably has to deal with them. But canker sores are surprisingly different from cold sores — and they're much weirder.
Canker sores are round, crater-like cuts that show up on the inside of your mouth and burn or tingle when you eat or talk, explains Timothy Chase, DMD, a dentist in New York City. They start off looking like little red blisters. Then they burst and turn into greyish-yellow sores that are usually about an eighth of an inch wide, according to the National Institute of Dental and Craniofacial Research (NIDCR).
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Despite how freakish they can look and feel, canker sores usually aren't a huge deal. And, according to the American Academy of Oral Medicine, about half of the U.S. population has them. So, as annoying as they may be, you're certainly not stuck dealing with them alone.
For the most part, you can manage canker sores with home remedies. The Mayo Clinic recommends trying a baking soda mouth rinse, dabbing a few drops of milk of magnesia on the sores, or just applying ice to numb them. If all that fails, there are a bunch of over-the-counter pain-relieving gel options (e.g. Orajel) that can make your mouth feel better while the sores heal. In more severe cases, canker sores can make it difficult to actually eat, so your doctor might prescribe painkillers or recommend procedures to cauterize the sores.
But why do canker sores show up in the first place? According to Dr. Chase, we don't have too many conclusive answers right now. But there are a few common triggers. First off, what you eat can make a huge difference: Certain spicy or acidic foods can bring on canker sores, Dr. Chase says, as well as chocolate, coffee, strawberries, eggs, nuts, or cheese. Eating these foods won't, on their own, cause a canker sore, he explains. But if you're already susceptible to sores, he cautions that they can definitely be the catalyst that makes one form.
Some studies also suggest that people with vitamin B12 deficiencies are prone to getting canker sores, and that taking a B12 supplement can prevent them from coming back. But, even if you're full up on B12 and you carefully avoid these foods, you can still end up with a canker sore.
That's because any sort of simple cut or break in the skin of your mouth — from brushing your teeth too hard or accidentally biting your cheek — can cause a sore to form, Dr. Chase says. That's one reason why people who have metal braces get them so frequently (the brackets can rub against their cheeks). In those cases, orthodontists recommend using wax to cover the part of the brackets that's scraping your mouth.
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Research has also found that using toothpastes and mouthwashes containing sodium lauryl sulfate (a foaming agent) can bring out canker sores in some people. The compound actually strips away a layer of tissue that would otherwise protect against the damage that causes the sores.
But some factors that contribute to canker sores are less obvious — including your genetics. Yep, recurrent canker sores are hereditary. So if your parents get them, there's a good chance you will, too. We also know that teenagers and young women are more likely than men to get canker sores, according to the Mayo Clinic. That's partly because some women get them during their period, which suggests there's a hormonal element to canker sores. Surprisingly, though, a 2009 study found that, although stress could play a part in their recurrence, it likely doesn't cause them on its own.
With so many potential triggers, it might seem like you can't win against your canker sores. But it might help to "track your foods, type of toothpaste, and activities that lead [up to your] breakouts," Dr. Chase suggests. That will help you identify patterns in your sores and give you clues about what to avoid. Steering clear of those factors can, hopefully, help reduce the chances that you'll get another breakout.
However, even if you think you've figured out your canker sores on your own, they're definitely still worth bringing up with your doctor — especially if you get more than three outbreaks per month. In some cases, frequent canker sores can be a sign of the aforementioned B12 deficiency or an autoimmune disorder, such as Crohn's disease or lupus. In these rare instances, your immune system goes after healthy cells in your mouth instead of fighting the viruses and bacteria, the Mayo Clinic explains, and you'll need specialized treatment.
But even if your canker sores are simply a sign of one too many Sriracha-topped meals, don't forget that your mouth is an important part of your health. And you shouldn't — ahem — brush off your symptoms or avoid going to the dentist just because you're shook.
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