Canker Sores & Allergies | Stop Canker Sores | Aphthous Ulcers | Allergy

Canker Sores and Allergies

by Allergy Guy

Canker sores, also known as aphthous ulcers, are a type of open sore that appears inside the mouth.  According to some, the cause is unknown, but sometimes there is a clear cause.

In this article we will look at what a canker sore is, what it is not, and some possible causes.  If your canker sores are triggered by one of these causes, then you have a good chance of eliminating canker sores.

Canker Soar AllergyA canker sore is a painful open sore that appears in the mouth.  It may be on the lips, side of the mouth, back of the throat or under the tongue.  It does not appear outside the mouth.  A typical canker sore is a couple of millimeters across, with a white bottom and an inflamed red rim.

This is not to be confused with a cold sore (herpes simplex 1) which appears as blisters around the outside of the mouth.

Canker Sore Causes

The cause of a canker sore or aphthous ulcer is not known, but there are a number of possible causes.  These include:

  • A small injury, such as biting the inside of your mouth
  • A reaction to citrus fruits
  • Vitamin b12 deficiency
  • Iron deficiency
  • Folic acid deficiency
  • Chemotherapy
  • Behcet disease
  • Crohn’s disease
  • Food allergies
  • Immune system reactions

The above is not an exhaustive list, but it does give you the idea that there are many possible causes of this condition.  On the other hand, a particular condition does not always produce a canker sore.

Allergies and Canker Sores

Some people with food allergies get a canker sore as one of their symptoms.  Some people have reported this as a symptom to nut allergies for example.

Allergies as a cause of canker sores can be hard to pin down.  If your allergic reaction is delayed, you may not make the connection with your symptoms and the food causing it.  Not all symptoms may appear at the same time.  Knowing this is the case, watch out for it.  You may discover that canker sores go away when you stop eating certain foods.

One study did show that a cow’s milk allergy can often cause canker sores.

Canker Sores and Toothpaste

Some types of toothpaste can cause canker sores for some people.  One reason is a common ingredient ( sodium laurel sulfate, see below) and another seems to be more specific to the types of toothpaste formulated to handle sensitive teeth.

Canker Sores and Sensodyne

If toothpaste such as Sensodyne is the cause, you may be better to have a dentist look into the cause of your sensitive teeth, and quit using the Sensodyne.

The ingredients in Sensodyne are as follows:

  • Potassium nitrate
  • Sodium fluoride
  • Strontium chloride
  • Strontium acetate
  • Potassium chloride
  • Titanium dioxide

Sodium Laurel Sulfate

Sodium laurel sulfate, a foaming agent, may be another cause of canker sores.  This is found in many brands of toothpaste.  If this is your problem, you will have to find a ‘natural’ brand of toothpaste (note that toothpaste is not natural, it has to be manufactured!).  Read ingredients carefully, the word natural is totally meaningless in the world of marketing.

Sodium laurel sulfate is also known as:

  • Sodium dodecyl sulfate
  • SDS
  • NaDS
  • Sodium laurilsulfate
  • SLS


There are many possible causes of canker sores.  One is allergies or chemical sensitivities.  If you get a lot of canker sores, pay attention to what you eat and how that correlates to your canker sores.  With luck you can find the link, eliminate the food or chemical, and live (mostly) canker-sore free and allergy-free.

See also Canker Sores And Hydrogenated Oils.

Thanks to wikipedia for the photo.

What is your experience with canker sores?  What seems to be the cause for you? Please leave a comment to help others manager their canker sores.

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{ 15 comments… read them below or add one }

1 kibby h January 7, 2017 at 17:47

I have 3 causes for my canker sores and they are all connected. First is a reaction to acidic foods, mainly anything with vinegar. Pickles, condiments, salad dressings, i avoid grapefruit like the plague. etc. Also, hormone fluctuations which is why more women get canker sores than men. And immunity problems. How are these all connected? Mold allergy. (Less so about the hormone issues) anything aged like vinegar, beer, wine, cheese. They grow mold. Even undetectable amounts. also, citrus often grow mold. when my hormones fluctuate, so does my immune system. And every once in awhile, like now, all of these happen at the same time and I end up with a dozen or more sores in my mouth and I’m completely miserable. Hormones fluctuate, I put too much mustard on my sandwich, I caught a virus, chest cold I think. And bam, canker sore explosion. All comes down to my mold allergy but its really hard avoiding ketchup and mayo and such. I can’t eat a burger without pickles. Anyway, I figured all this out without a doctor. I’ve never seen a Dr about my allergy or canker sores.


2 Deb February 1, 2016 at 15:51

I’ve had recurring problems with canker sores since having full dental implants. I’ve found that a strong stannous flouride rinse solution of .63% will heal a developing sore within a couple of days. Several brands can be purchased on line–I now always keep a bottle in my medicine cabinet!


3 Faye February 16, 2015 at 01:36

I’m having canker sore problems, at first I thought it was the yeast, bread, wine and beer, have yeast but now I think its simply from the alcohol. I’m not sure if all alcohol has yeast ingredients. but I find myself having the problem after drinking alcohol.


4 Mel October 24, 2012 at 23:21

I have a huge canker sore at the moment – it starts way back underneath my tongue (near where my tonsils use to be) and up the side of my cheek. I went to see the doctor yesterday as I felt it wasn’t getting any better after a week. He said it looked infected and prescribed an antibiotic. I hope it works as not only is it painful it is making my mouth taste disgusting. And guess what? …. I have been using a foaming Sensodyne toothpaste!! That is now going in the bin!


5 Allergy Guy October 25, 2012 at 19:44

Let us know if the canker gets better after you stop using Sensodyne. It causes me problems, which doesn’t mean to say it causes everyone problems. It would be a nice easy solution for you so I hope it works.


6 Marsha May 25, 2012 at 02:05

Well I currently have a canker sore on the back of my tongue which hurts so bad, one on my lip, and I have like a boil on my chin. I feel like my face is in so much pain I am gonna take some tums, benadryl, and some pot and see if that helps? I know they say that its only canker sores but I think the boil was caused by the sores because I found a way to relieve the pain on the sore on my lip but when I do that it usually moves the sore someplace else so now its not helping its just moving it someplace else. I am going to try and reduce the acid in my body thanks for the input I am in so much pain. I wonder if pain killers cause acid in the body?


7 Jill Leng August 8, 2011 at 22:06

I did some research a few months back about canker sores because I was getting so many… up to eight at once. Nuts kept surfacing as a major cause so that was the first thing I eliminated. Sure enough, my mouth was clear in no time. I tried to reintroduce them and I immediately got them again. So happy to have found the answer for me.


8 Adam June 23, 2011 at 15:42

I find that I get canker sores when the acid count in my body is too high; like if I have had too much citrus. When I get a canker sore I just drink a glass of buttermilk and the sore goes away in a few hours. The buttermilk acts as a base and neutralizes the acid. I’ve been doing this since I was a child so I’m used to the taste, but most people would rather suffer with the sore than take the cure.


9 Allergy Guy June 23, 2011 at 17:05

There are many other ways to neutralize acid in the body besides buttermilk, so there must surly be other cures that are more palatable to some.

Another approach is to reduce acid-forming foods.

Thanks for your insight about pH in the body. I’ll see if I can find out more about this.


10 Margery Strom May 3, 2011 at 21:09

The treatment for a cancer sore prescribed by a reputable physician years ago consists of the following:
Purchase a “shaving pencil” at the drug store
At home
Prepare an 8 oz glass of warm water and add 2 teaspoon of table salt.
Moisten the tip of the shaving pencil in tap water and apply firmly to the cancer sore, and NOT adjacent tissues
Hold the pencil in place until uncomfortable THEN remove and rinse your mouth thoroughly with the salt water solution. This stops the chemical reaction.
In a few minutes you will no longer be aware that you ever had a problem.
In a few instance the treatment may have to be repeated.


11 Allergy Guy May 3, 2011 at 22:18

Thanks for that remedy, Margery!

I’ll try it next time I have a canker sore.

By the way, what is a shaving pencil?


12 Margery Strom May 4, 2011 at 07:51

A Shaving Pencil, so called as it is used when a cut occurs when shaving with a blade razor. It is also called a stryptic pencil, and contains a caustic substance that when moistened, and applied to skin or mucous membrane, causes a chemical burn. This is what happens when used on a cancer sore. The salt solution neutralizes the reaction and stops the burning. The 20 – 30 seconds of discomfort (during the application of the pencil ) out weigh the days of problems.


13 Allergy Guy May 4, 2011 at 08:35

Thanks for the clarification, Margery.


14 J-Mom April 29, 2011 at 09:04

I’d like to add that stomach acid, as well as acid in foods, seems to cause canker sores.


15 Allergy Guy April 29, 2011 at 12:42

Stomach acid, as in acid reflux?

As for acid in foods, this may be possible, but it is not common, and may work in conjunction with other causes.


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