Cause of canker sores
Sodium Lauryl Sulphate
There is no definitive underlying cause for these annoying sores, but experts say there are several things that contribute to their always untimely arrival, including acidic foods, food allergies, menstruation, heredity, impaired immunity, mouth injuries, and some chemicals, especially sodium lauryl sulphate (SLS), which is found in most commercial toothpastes. SLS is also a common ingredient in some "natural" toothpastes, such as Tom’s of Maine.
However, all of these factors are secondary triggers and not the primary cause. The primary cause is unknown but likely from multiple sources.
Doctors and scientists who study such things have developed several theories about the initial, principal cause of canker sores, but there is still no consensus.
In my view, few of these would be a concern if you stopped using toothpastes with sodium lauryl sulphate. SLS opens the door for the other contributing factors. This is evidenced by their gradual disappearance upon changing toothpastes.
Choose a toothpaste that won't trigger canker sores.
Bacteria
There is some evidence suggesting that canker sores are an immune system response to a certain bacteria in the mouth. Some researchers think they're caused by an oversensitivity to hemolytic streptococcus bacteria.
One possible reason for this conclusion is that some people get relief and faster healing from anti-microbial mouthwashes, such as those that contain tetracycline.
On the other hand, it may be that bacteria that already exists in our mouths merely interferes with the healing so that killing them allows the sores to heal faster.
Acidophilus: an easy way to handle canker sore causing bacteria.
Using mouthwashes against oral ulcers. They can help, but...
Mouth Injury
Mouth injuries from accidental biting, trauma from sharp objects such as braces or food such as chips or pretzels can all lead to canker sores.
Accidental biting might be a tertiary cause because a food allergy can make mouth tissue swell slightly such that it gets in the way enough to be bitten. The secondary cause in that case is sodium lauryl sulphate (SLS) which paves the way for canker sores to form right on the injured spot. Without SLS, mouth injuries heal more easily.
Why does SLS lead to mouth sores?
Stress
Some people report that periods of increased stress cause their canker sores. Stress can tax our immune systems and give opportunistic microorganisms a chance to wreak havoc. Excess stress can also lead to autoimmune disorders.
Ted Grossbart, Ph.D., a Harvard Medical School psychologist notes on his website that "Emotional stress is the most commonly cited precipitant..." for canker sore recurrences.
Food Allergy
Just as people can be allergic to pollen and pet dander, they can also be allergic to the food they eat. The bad part is that some people tend to develop sensitivities to the things they eat most often.
Food allergies vary with the individual, but there are a number of common foods that could trigger mouth sores.
What should I do when I get a canker sore?
For immediate relief of an existing mouth ulcer there are a number of things to do. There are treatments to alleviate the pain and other potions that will speed the healing. Of course, the most important remedy is the one that will prevent the sores from returning.