Causes of Mouth Ulcers
Number One Cause?

What are the causes of mouth ulcers or canker sores?

To be honest, nobody knows for certain. It seems to be a combination of things. This potential trigger combination is different for different people. BUT there is ONE thing that seems to be very common. Read on to find out more.

Canker sore causes do not seem to include a virus infection or a bacteria infection. However, it is possible that some folk may have a certain type of allergic reaction to a particular bacteria in their mouth.

Close up of two ulcers on a lower lip


The causes of mouth ulcers may also include a food allergy. This can be a difficult one to pin down, as the particular substance causing the allergy usually occurs in several foods, and perhaps only in some brands but not others!


There is some medical research that suggests that for some people, the causes of canker sores in the mouth may be what is called an auto immune disorder. What happens here is that your own immune system mistakenly attacks normal cells of your tongue or cheeks. So it's not an infection or disease, it's your own immune system that is causing the damage!

The Causes of Mouth Ulcers


Other dental research has established a link between mouth ulcers and a particular ingredient in just about every toothpaste on the market. It's called sodium lauryl sulfate, and it's added to toothpastes to make them foam up a bit. Check the ingredients of your shampoo bottle - it's in there too! But in some people it can trigger ulcers or canker sores.

It is usually shortened to SLS. One of the best toothpastes that is SLS-free is from Therabreath.

Another one is Tom's of Maine toothpaste.


Some other research studies in the United Kingdom show that about 20% of patients get canker sores due to problems to do with nutrition. A lack of iron, vitamin B 12, and folic acid, are the usual suspects. Vitamin C can also play a role, as it is involved in the absorption of iron.

These nutritional causes of mouth ulcers can come about in 3 ways;

  • If your diet is very low in some vitamins or minerals, you simply aren't getting enough through your system!
  • Your diet may be fine, but you may be having a problem absorbing the vitamins and minerals that you are eating.
  • A very small number of patients may get canker sores as part of general digestion problems, such as an inability to digest certain cereals, or if they have had surgery to remove part of the bowel.

Sometimes you can overcome these problems by taking a high enough dose of a quality vitamin and mineral supplement.

In these cases above, you should get some tests done at your doctor's office, so that you know what it is you might be lacking! Then your doctor can recommend or prescribe the best supplements for you.

It's obviously important to take the correct vitamins and minerals that you are lacking, but it's also very important to get a high-quality supplement that will be absorbed as well as possible.


In people who are prone to getting mouth ulcers, stress can bring on an attack. They may tend to get ulcers anyway, but a particularly stressful time at work or in the home can trigger more frequent and more extensive ulcer formation.

In these instances, a herbal remedy such as Passiflora or St. John's Wort may help, but they usually take a while to become effective. The best method is to start taking them before you get any ulcers, if you are going through a particularly stressful time.


There may be a hormonal factor, too, because many women only get canker sores in the mouth during certain phases of their monthly cycle. Also, a lot of women who regularly get aphthous ulcers seem to have a big improvement when they are pregnant. Hormone therapy has been used to treat some women, successfully.

As you can see, there are many possible causes of mouth ulcers, and some of them need to occur together! But I recommend you check your diet, and look for a SLS-free toothpaste.

Here is another page about mouth ulcers that may be useful;

Mouth Ulcer Treatment

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