One of my biggest pet peeves in life is when I get a canker sore. I got more canker sores than I could count when I had braces, thanks to the grating metal brackets stuck in my mouth. But while I hated the irritation caused by the sores, I never realized that my diet could have been influencing my tendency to get them.

Before I list a few of the major canker sore-causing foods, let’s make sure we’re on the same page when it comes to canker sores. According to Livestrong.com, canker sores are small, painful ulcers that appear inside your mouth and along your gum line.

Unlike cold sores, which appear around your mouth, canker sores cannot be passed on via physical contact and gradually disappear within a week or two. Though canker sores can be caused by physical trauma (like the constant rubbing of braces against the gum line), your diet plays a key role as well.

Now that we’ve covered the basics, let’s move on to the primary canker sore culprits.

1. Citrus Fruits

canker sores

Photo by Claire Waggoner

Citrus fruits like oranges and lemons are notorious for worsening existing canker sores. The citric acid in these fruits may actually cause you to develop more canker sores, which is why you should avoid ingesting citrus fruits and juices when you have an active sore.

2. Coffee

canker sores

Photo by Gabby Phi

I know it’s difficult to hear, but your daily cup (or three) of coffee might be causing your canker sores. Coffee contains salicylic acid, which can irritate the sensitive tissue of your mouth and cause those annoying sores to pop up.

3. Tomatoes

canker sores

Photo courtesy of Tony on Flickr

Like coffee, tomatoes are rather acidic and can cause canker sores to spring up (are you noticing a trend yet?). So you can kiss your favorite pasta sauce and tomato soup goodbye, at least for a little while.

4. Strawberries

canker sores

Photo by Claire Waggoner

Like everything else up to this point, strawberries are—you guessed it—slightly acidic, which is why you should avoid them if you’re prone to developing canker sores. Do yourself a favor and say no to mom’s famous strawberry rhubarb pie; it’s just not worth it, kid.

5. Chocolate

canker sores

Photo by Emily Hu

Canker sores generally develop if you have a chocolate allergy—yes, that exists, and yes, it sounds terrible. Luckily, your sores are likely because of an allergy to one of chocolate’s components (such as milk, soy, or tree nuts), meaning you can still snack on your favorite sweet treat if you find a brand that caters to your allergy.

With that said, you could also have an allergy to the actual cocoa beans. In which case, you’re totally screwed.

6. Spicy Foods

canker sores

Photo by Wendy Zhou

Much like acidic foods, spicy foods containing hot peppers or other irritating ingredients can cause an outbreak of canker sores. You likely don’t need to give up spice completely if you just take your favorite curry down a notch. On the plus side, less spice means you’ll be able to actually taste the food better. 

7. Gluten-Filled Foods

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Photo by Emily Hu

If you get reoccurring canker sores, you might want to visit your doctor to see what’s up. If you’re sensitive to gluten or have Celiac disease, your body may respond by producing canker sores. The damage done to your intestines affects other soft tissues in the body, which results in sores inside your mouth. Some researchers think this occurs because of a vitamin deficiency caused by your intestine’s impaired ability to absorb nutrients, but they’re not 100% positive why this happens.

8. Soft Drinks

canker sores

Photo by Jared Sebby

Soda is loaded with corn syrup and phosphoric acid, which promotes inflammation and leads to canker sores. Switching to diet drinks won’t help your case either, as diet sodas are also acidic. In addition to causing canker sores, soda has been shown to erode enamel over time, which is a whole other beast you never want to deal with.