They are, truly, the worst. Here's how to deal.
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If you've ever had one of those painful blisters in your mouth that makes everything from chewing to brushing your teeth feel awful, then you know that canker sores are no joke. They show up out of nowhere and it often feels impossible to get rid of them or relieve the pain.

Sure, you could endure the ache for a week or two and pray it goes away before you accidentally bite it again — but there's also a chance that another could appear at any moment, and you'll have to deal with the irritation all over again. A better plan? Learn how to get rid of canker sores, what you can do to prevent them, and how to relieve the pain while you're dealing with one. Here's what you need to know.

What Is a Canker Sore?

"A canker sore is an aphthous ulcer (small lesion or wound) found inside the mouth, usually on the tongue, soft palate (the soft part of the roof of your mouth found toward your throat), and inner cheeks," says Sharona Dayan, D.D.S, D.M.Sc., a periodontist at Aurora Periodontal Care in Beverly Hills. Canker sores are raised sores that are usually red, but sometimes have a white or yellow center. "They are not contagious and can be very painful," says Dayan. "Canker sores are usually small but can sometimes grow to 1 cm in diameter." They're generally caused by irritation or injury to the mouth — and aren't associated with any virus or bacteria — though the cause of canker sores isn't totally understood (but more on that in a sec).

Canker Sores vs. Cold Sores

Canker sores and cold sores are often confused for each other, but while they have similar names and somewhat similar symptoms, they are not the same thing.

Cold sores are a form of the herpes virus and usually are found on your lips and around your mouth. They are sometimes mistaken for pimples as they are typically red and blistered, sometimes having a white or yellow center. They're often painful and will burst after a little while, leaving you with an open sore that will scab over.

They can appear in small clusters and may be filled with fluid, says Cindy Roark, D.M.D., M.S., SVP and chief clinical officer at Sage Dental. "Cold sores are related to the herpes simplex virus-1 and tend to be highly contagious," says Roark. "They can be spread among family members from sharing utensils, towels, or razors." They can also spread by kissing.

Generally, if you have a sore outside of your mouth, it's probably a cold sore and should be treated as such. If it's inside, it's likely a canker sore, and the good news is that they aren't contagious. If you've been kissing or sharing drinks or personal items with someone that has canker sores, there's really no need to worry about them being passed onto you (or vice versa). The bad news? Canker sores can be caused by about a million other things.

What Causes Canker Sores?

More meh news: It's unclear exactly why canker sores happen, says Roark. Because many different things can cause canker sores, it makes it difficult to tell why any specific person gets them or doesn't. That said, there are factors that could contribute to them: "Risk factors such as stress, fatigue, allergies to citrus and highly acidic foods or toothpaste, hormonal changes, or vitamin deficiencies usually play a part," she says. "They can also come from an injury, such as biting the cheek or braces rubbing." Excessive rubbing or biting on the cheeks tends to irritate them and can cause small cuts, leaving room for a canker sore to form.

It's common for people who eat lots of acidic foods (such as citrus, sugar, and even dairy), spicy dishes, or salty, crunchy foods to get canker sores. If you frequently drink carbonated beverages, coffee, or alcohol, it can act as a trigger, too.

Some people may also have allergies to specific ingredients in toothpaste, such as sodium lauryl sulfate. A toothpaste allergy may also manifest itself through constantly chapped lips, swollen gums, or a rash around the mouth, according to research. So, if you experience these symptoms along with canker sores, see a doctor to determine if an allergy is your main issue.

And for those with a uterus, the hormonal changes that happen around your period can bring on canker sores, specifically due to an increase in progesterone hormone levels, according to research done by the Cleveland Clinic. Higher progesterone levels before and during menstruation may directly cause canker sores or may cause gums and salivary glands to swell (which, in turn, can increase your risk of accidentally biting or irritating the inside of your mouth).

How to Relieve Canker Sore Pain

Luckily, there are treatments that can help relieve some of the pain from canker sores, says Tina Saw, D.D.S., founder of Oral Genome (a dental testing kit).

Canker sores can be relieved by over-the-counter ointments and creams containing benzocaine (such as Anbesol, Kank-A, Orabase, or Zilactin-B) and fluocinonide (such as Lidex, Vanos) or mouth rinses containing dexamethasone and/or hydrogen peroxide (such as Orajel Antiseptic Mouth Sore Rinse, Peroxyl), says Saw. "These can all help reduce pain and inflammation," she says. Her advice for those choosing an over-the-counter product is to look for the American Dental Association Seal of Acceptance. "Those products have undergone and met the ADA criteria for safety and efficacy," she says.

Roark agrees that using gels or rinses can help with the pain and healing process. "Orajel 3x Medicated is my new favorite over-the-counter medication for patients," she says. "It can be used on all ages from 2 years old and above and has benzocaine to take the pain down."

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She also recommends ioRinse (Buy It, $40,, as it has very few side effects, making it safe for almost any patient. "In fact, we have every patient rinse with it pre-procedurally because it is effective against viruses (including the coronavirus and rhinovirus), bacteria, fungi and spores," she says. "You will see this product more and more in dentist's offices because there just isn't much it won't kill and almost no tissue it won't heal." (Related: Can Mouth Wash Kill the Coronavirus?)

If you decide not to use an ointment or rinse, canker sores will still heal on their own, taking up to two weeks to completely resolve. While waiting for them to heal, it's still a good idea to avoid eating or drinking highly acidic, salty, or spicy foods and drinks as they may trigger inflammation and make the sores stick around and hurt for longer. You should also stay away from carbonated beverages and alcohol — including oral products, such as mouthwash, that contains alcohol.

If you have a canker sore that's extremely large or sticks around for more than a couple of weeks, you'll want to see a dentist as soon as possible to find out if it's infected or is the result of a more serious underlying problem. A dentist may also be able to use a special laser to treat a problematic canker sore. (Related: The Best Toothpaste for Bad Breath)

How to Get Rid of Canker Sores

Since the exact cause of canker sores is unclear, it can be tricky to get rid of and prevent them. A BMC Oral Health study found evidence that hyaluronic acid-based treatments, which can include gels or oral rinses such as Gengigel (Buy It, $15,, may promote quicker healing of canker sores, but it may not work for everyone. If you want to get an idea of what's causing canker sores for you specifically, it'll require some detective work.

Take note of when your canker sores appear — do you often get them before a school test or big work presentation? You might have stress-induced canker sores. If you get them consistently, then it might be due to something in your daily diet or a product you use often, such as ingredients in your toothpaste. Shifts in your hormones could also be causing your canker sores, which may be noticeable while you're on your period. Pinpointing the cause might take from trial and error, but it can help you prepare for and know when to expect them or to avoid the things that trigger canker sores in the first place.