Monday, June 24, 2024
HomeDental Disorders & DiseaseTen Causes of Canker Sores

Ten Causes of Canker Sores

Ben, an Oral Answers reader, recently asked about what really causes canker sores (also known as aphthous ulcers.) He’s heard that sodium lauryl sulfate in toothpaste can cause canker sores, but not everyone who brushes their teeth gets canker sores.

Canker Sore
A canker sore on the posterior roof of the mouth

To be honest, there isn’t any one thing that can cause canker sores in everyone.  However, different things can cause canker sores in different people.

Here’s a list of 10 things that have been shown to cause canker sores in certain people.

10 Things that Cause Canker Sores In Susceptible People

1. Allergies

The book Oral and Maxillofacial Pathology by Neville says, “An antigenic stimulus appears to be the primary initiating factor in the immune-mediated cytotoxic destruction of the mucosa in many patients.”

Basically, it says that the main factor that causes the body to destroy it’s own oral tissues appears to be an allergic response.

There are a LOT of different allergens that have been associated with canker sores.  Here’s a list of the most common ones:

  • Sodium Lauryl Sulfate (SLS), commonly found as a main ingredient in toothpaste
  • Certain medications such as NSAIDS (ibuprofen), beta blockers, and nicorandil
  • A variety of foods, such as:
    • Citrus fruits
    • Strawberries
    • Tomatoes
    • Coffee
    • Gluten (the protein found in wheat products)
    • Dairy products, such as cow’s milk and cheese
    • Nuts
    • Chocolate
    • Food dyes
    • Food flavorings
    • Food preservatives

It’s important to remember that many of the foods listed above do not usually cause canker sores, but they have been found to be trigger foods in certain people. If you think that a certain food is causing your canker sores, you can try to pinpoint which food it is by using the above list and trying an elimination diet.  You will want to talk to your doctor about your concerns to get additional information before attempting to eliminate certain foods altogether.

2. Stress

Stress is a major cause of canker sores.  It is presumed that since stress weakens the body’s immune system that it makes it more susceptible to canker sores.

3. Trauma

Trauma has also been associated with canker sores.  Anytime the barrier over the deeper tissues inside your mouth is broken, there is a higher risk for canker sores in certain people.  The trauma can be caused by a variety of things, such as sharp foods like chips and crackers, biting, braces or hard=bristled toothbrushes.

4. Genetics

Your family history can play a big role in whether or not you get canker sores.  In fact, if both of your parents get canker sores, there’s a 90% chance that you will get them too!

Joseph A. Regezi, in his oral pathology book states, “Family history represents a risk factor. Over 40% of affected patients have a first-degree relative who is also affected by aphthous ulcers. There is a 90% degree of risk when both parents are affected.”

5. Compromised Immune System

Some people who have problems with their immune system have many canker sores.  For example, people with AIDS (Acquired Immunodeficiency Syndrome) frequently get aphthous ulcers.

6. Infectious Organisms

Certain organisms have also been implicated in causing canker sores in certain people.  Some examples of organisms that are associated with canker sores are:

  • Certain forms of streptococci
  • Helicobacter pylori
  • Herpes simplex virus
  • Varicella-Zoster virus (chicken pox)
  • Adenovirus
  • Cytomegalovirus

7. Nutritional Deficiencies

Nutritional deficiencies have been shown to be correlated with canker sores.  Shortages of the following vitamins and minerals are suspect:

  • Iron
  • Folic Acid
  • Zinc
  • The “B” Vitamins (Vitamin B1, B2, B6, and B12)

8. Stopping Smoking

When you smoke, the tissue lining the inside of your mouth gets slightly thicker.  Quitting smoking thins the lining inside of your mouth and makes you more susceptible to canker sores.

This doesn’t mean that you should smoke to avoid canker sores!  Smoking has many more serious negative effects on your oral health.  For example, smoking has been linked to oral cancer and smokers in general have less teeth than non-smokers.  So it is still a great idea to quit smoking if you currently do!

9. Hormones

Hormones can also affect whether or not you get canker sores.  The book Oral and Maxillofacial Pathology by Neville says, “In a small subset of female patients, a negative association was reported between the occurrence of [canker sores] and the luteal phase of the menstrual cycle—a period of mucosal proliferation and keratinization.”

The luteal phase of your menstrual cycle begins right after you ovulate (approximately day 14) and ends on the day you get your next period.  When the tissue inside your mouth gets thicker (i.e. – more keratin forms) then you see a decrease in the amount of canker sores.

10. Blood Abnormalities

Certain blood abnormalities, such as cyclic neutropenia have also been implicated in canker sores.  Regezi’s Oral Pathology textbook states the following (I bolded the part that deals with canker sores):

“Cyclic neutropenia, a rare blood dyscrasia, is manifested as severe cyclic depletions of neutrophils from the blood and marrow, with a mean cycle, or periodicity, of about 21 days…Fever, malaise, oral ulcers, cervical lymphadenopathy, and infections may appear during neutropenic episodes.”


There are a variety of things that can cause canker sores.  However, you may notice that nothing I mentioned above applies to you and you still have canker sores.  This is because we still don’t know everything that causes canker sores.  Researchers are still working to understand the exact reasons why some people get them and some people don’t.

Do you get canker sores?  Have you noticed that they are caused something that I didn’t mention above?  I’d love to hear your comments and questions in the comments section below.  Thanks for reading!



  1. I just recently had a gold crown put on my implant and directly in front of my gold tooth a canker sore developed where the inside of my lip rests on the gold crown. The only other time a canker sore developed is when the implant doctor pulled my lip out with one of his stainless steal tools and t he spite developed right where he had the tool positioned on the inside of my lower lip.

  2. I’ve noticed in the past year that I get canker sores the week before my period starts. It’s almost to the day. It always starts with me accidentally biting my lip and then I put two and two together and notice its a week before my cycle starts. It doesn’t happen any other time during the month. I’ve consulted my primary care physician and she claims its due to hormones and/or the stress on my body during that time of the month. My gyno had no idea an had never seen a patient with the same issue (not so fun to hear from a medical professional!) My physician prescribed me the same medication that people use during herpes break outs. I was told to take two pills in the morning and 12 hours later another two on the onset. But the pills haven’t been helping. The canker sore still takes over a week to fully go away. It’s so frustrating to have two weeks out of the month that I’m in pain! Wish I knew why it was happening exactly and if I could fix it! I’ll take any suggestions!

    • That sounds like the type of canker sore caused by a folic acid deficiency. If you also have darker skin under the eyes, that’s another symptom of folic acid deficiency. I used to get them and noticed that they would stay away when I ate a lot of dark green leafy vegetables. And a vitamin C supplement can help the absorption of the folate. Canker sores are not related to cold sores/herpes, so I think you shouldn’t follow that type of treatment. It’s really stupid that our medical doctors are not trained in nutrition.

    • Same happens to me before I start my period or when I’m extremely stressed out. Food grade hydrogen peroxide works for me. I just swish it around my mouth gently a few times a day and after about 3 days they are gone. If I don’t have that I put baking soda on the sores. Hope this helps!

    • Hello I can recommend to take some B12 and vitamin C tablets…if you can find Becoyzme C might help. You might see the benefit from this so quickly and it will also boost your immunity.

    • Ugh! Me too! It starts as a tiny bubble on the inside of my lips or cheeks and just progresses. It even seems to spread out into another one. I just smoke a little weed to de-stress and relax and I seem to forget about it. But I have to tell you, that I use a big ice cube to make the pain go away, and to stop the pulsing and enlargement. It seems to work. I can always tell when I am going to have a cold sore or a period because I wake up in the morning with a really downtrodden feeling like crap really. I know others who get the same thing.

  3. To kristen: Upon making my own research i ran across a constion called APD- Auroimmune Progesterond Dermatitis/Stomatitis. I took pics to an endocrinologist. I get recurrent canker sore outbreaks every week before my period and just recently started getting granuloma annullare, a skin rash when I took a birth control
    Pill. Upon the dr researching the info I brought to her she diagnosed me with APD. It is not really heard of. Look into it.

  4. Since having a Motorcycle wreck 5 years ago, I have them just about every two weeks I pretty much count the times I don’t have them rather then the times I do just as one start to fade you can feel another starting Now I was a 35 year smoker that I don’t anymore, but also was on a ventilator and now have Titanium in my body someone stated that he had a new Polio shot and it stop his

  5. Three day later canker

    Chocolate for me triggers a three day later canker. It is very difficult to detect this allergy to chocolate and nuts. You see the chocolate swells the tongue and inside of the cheeks and because they are bigger due to swelling, your teeth abrade and damage the sides of the tongue and the insides of the cheeks and lips while chewing.

    The three day lag makes it difficult to make the association to chocolate.

    A several day long malaise follows the canker onset. I feel terrible.

  6. Hi Dee.
    Consider your diet. Are you eating healthy food and getting all the nutrients you need? See my post dated August 7, 2014 about the link between canker sores and folic acid (B vitamin) deficiency. If you don’t eat leafy greens, add them to your diet and take a vitamin C supplement. And of course, consult your doctor–maybe some lab work is needed. I hope it gets better! Take care.

  7. I drank mefenamic acid for the pain from my tooth extraction but had an allergic reaction. My upper lip was swollen and the roof of my mouth has a bit swelling but the pain is a 10 especially when I eat or drink. The swelling of my upper lip subsided after one day, but the pain at the roof of my mouth is still there. I have already experienced this before but did not think it was an allergy due to the medicine because the pain was dull and bearable now it is more painful. From my research, it points out to canker sores. what can I do to make it go away?

  8. I’ve had fairly frequent canker sores off and on for as long as I can remember. Since delivering my baby 4 months ago, I’ve had them pretty much nonstop. As soon as one heals, I have another. I tried switching to a SLS free toothpaste with no relief. I take a prenatal MV daily and I am still breastfeeding, so I’m convinced it’s related to hormones.

  9. I think I finally figured out when I get one, right after I drink out of my stainless steel cup. I know that sounds weird but I had lost the cup and hadn’t had a canker sore, found and drank out of the cup, by the next morning I had one. I’m drinking water out of it, not coffee.

    • I think you’re onto something there! I just started to get some today, and realized I used my stainless steel cup for coffee this morning. I hadn’t used mine for a while, because my sister gave me a new mug, but I decided to use the stainless steel one this morning. Also, I just started my period. I’m gonna try not to use it for a while. Thanks!

  10. Sugar. In any form. I can have a piece of cake or pie or a cookie once in awhile canker free but never twice in the same week. Also any form of fruit will effect me the same way. I also get pretty hefty body aches the next day if I have too much sugar in one day. I have to use straight baking soda to brush my teeth. Even the ‘healthy’ toothpastes give me sores. I saw a series of messages about 5 years ago where eight people reported the same thing. Nothing lately.

  11. Unfortunately, I am confident I have over 15 sores on my tongue alone!! Currently, my lymph nodes are as large as a North Korean ballistic missile, but fortunately, my lymph nodes are more dangerous (for the time being!! Haha). Here’s the issue, I am currently prescribed 800mg ibuprofens (when needed), I am currently under tremendous stress w/ holidays, EOY work stuff, family visiting all over, but the coup de gras is that I’m currently in throws of a MAJOR acute simusitis w/ bronchitis attack. Due to many reasons, most listed above, I had avoided the doctor. Everyone in my family had a cold 10 days ago & I assumed that pesky thing finally got me – the timing was right and the symptoms were nearly identical. Well, 7 awful days later, a trip to the ER w/ breathing problems and chest pains put an end to the wait.

    Now I’m currently on 7 different prescriptions, not to mention the over the counter stuff for the excruciating mouth pain associated with the cankers. I’ve always gotten them – my mom has, too, so that’s expected but they seem to be gaining major steam both in numbers of them at once time AND the severity of the pain.

    I am using (3) different pain remedies: (1) Ora-gel type, a newer “stick” I’ve never seen before (think thin magic marker) called Kank-A SoftBrush Gel for specific spots & the God-send spray for the whole general area including my throat, chloraseptic!!

    Sorry for the long answer, but without major investigations, I’m sure that there’d be no way to zero-in on what is the deal.

    I think this current “bumper crop” is associated with sickness coupled with LARGE amounts of stress – no different than anyone reading this!

    (My apologies for any errors above, as I typed this on my iPhone while battling said cankers & sickness & I sincerely refuse to bother with it. My voice has been gone for a week, so I’ve decided to take it out on the print world!!! Y’all are the sufferers of my wrath!!)

    • I enjoyed your wrath, it’s nice to see others that find difficulty foregoing the temptation to just simply “Leave A Reply”

      Attempts to say thanks to a refund from a wireless was reflected by some terrible character counter evil!!! Perhaps you also share this hatred?
      In a bath, relieving stress, on my phone which I dropped into the bath yesterday “note 5″ … and works today! Thanks to the east and rice. I never sent my thanks last night, to the phone people.. I’m curious, what do you do for a living? Perhaps we have some need to get this out so instead of running 6000 miles over the weekend we just make a short reply novel .. For everyone else, { I thought it was herpes virus..? I’ve been ashamed but also forgiving in what my parents said was genetic, but also from my papa who might mom thought had gotten around a bit before marriage. ABOUT CANKER SORES
      When I’m stressed I get then. But only a particular response and stress. Sometimes I bite my cheek and I know! Other times I fear but then forget. There us one thing, for the few that found times theif this evening by reading up till this one secret… ( when I lived in Colorado I never once had a canker sore…..!”””””
      Yes. Weed!? nor until i moved to “misery” land did they come back. Yes, stress induced. But ive since remembered, and my cure is upon onset, smoke a bowl or several and have the evening to yourself. All my muscle pain gone too as a plus. I’m more high strung than I know. It’s not easy convincing yourself and others about the missed |||||| omg. I’ve got to get out of the bath. One sentence I said!!!!! So the cure for me is a relaxing evening alone. Preferably a series. And a good joint or bowl. Sleep will come. Attachments get lost, habits are forgotten, things are finally questioned .

      • I think you’re right, David! I live in Colorado now, and when I smoke some weed, it totally de-stresses me. I have always believed I am type-A personality, but when I can smoke some weed and relax, I can actually be a calmer mom, a better wife, concentrate longer on one thing, and just not take life so seriously. It really helps. Too bad people take prescription drugs to do the same thing. When I get stressed out, I bite my cheeks too, and the sad thing is, I have seen my 10 year old doing the same thing. She is taking after me a bit. I just hope she doesn’t become as high strung as me. I also eat better, because I am more conscious of what I am eating, and salad with a tangy dressing is the BEST! Spending time with my 4 year old is so much more fun too. You can just put yourself on their level and not think about all the things you have to do; like household chores, the bills that have to be paid, or other things that stress you out. Too bad people have their preconcieved notions about weed. Honestly, the world would be a much better place if more people smoked weed. .. Just a note also, I think Charlotte is onto something there. I used a stainless steel coffee cup too, and I just had a lightbulb moment when she said that. Maybe the stainless steel in combination with the arginine, or heat stresses the lining out in my mouth. I’m gonna try to avoid using it and see what happens.

  12. After being prescribed a high dose (3200 mg) of ibuprofen to control inflammation after a knee replacement, I started having canker sores. Now whenever I take even a small dose of ibuprofen the sores return.

  13. High fructose corn syrup for me! I have had this theory for years now and tested it many times — whenever I have more than just a little bit, I inevitably get one. Also, as others have said, it almost always happens a week before my period and lasts throughout. I’m dealing with two now.
    Does anyone else notice beer makes it feel much better? Not getting drunk, I mean specifically beer. Wine/mixed drinks don’t help.


    Am from the north Carolina. I caught genital herpes from my ex boyfriend who never had any symptoms of herpes . I had it for 4 years and it has literally affected my life before I got cured. People think herpes is really a minor skin irritation, herpes has long term effects on health. The stigma attached to this virus by ignorant people is ridiculous. Most people have herpes in one form or another but they might not be aware of it. I would like to advise people on how I got rid of my herpes by using Dr Sikies medicine. I saw a comment posted by a woman from Ireland on the internet that she got rid of her herpes with the help of Doctor Sikies and I was so happy when I saw that post. I quickly contacted doctor sikies regarding a cure for herpes. I explained things to him and he assured me not to worry that he will cure me. I ordered his medicine which was sent to me via DHL. i got the herbal medicine and i used it as i was told for the period of 2 weeks which is twice a day ( morning and at night before going to bed) .after 2 weeks, i found out that the herpes was no more and this was also confirmed by my doctor. If you have herpes or other similar disease and you want it cure, kindly contact Doctor sikies WhatsApp / Email Dr Sikies can also cure HIV, stroke, ulcer, depression, autism, cancer, diabetes etc.
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