Canker Sore Causes You Need to Know

Canker sores (mouth ulcers) are ulcers that occur within the mouth. Since canker sores are incredibly painful, it’s natural that you would want to do everything in your power to avoid them. Of course, avoiding canker sores first begins with being able to identify them as well as understanding their most common causes.

Canker sores look like small white or reddish holes on the inside of the lips, under the tongue or along the gum line. They typically start out pink or reddish in color and then, as they progress, turn white. So, just what causes these pesky sores, anyway? The first cause on our list affects more than 50 million people in the United States each year…

How Stress Causes Canker Sores

What is the main reason why stress causes canker sores? Stress leads to a buildup of certain hormones. These hormones can end up causing reactions in delicate tissues of the body, such as the gums and inside the lips. The result? You probably guess it: canker sores.

The following cause of canker sores might be part of your twice-daily teeth-cleaning routine…

Toothpaste With Sodium Lauryl Sulfate

Almost all toothpaste these days contain sodium lauryl sulfate, meaning it could be contributing to many folks’ canker sores. Sodium lauryl sulfate is a chemical added to toothpaste and other cleansing agents, largely for its foaming properties. When you brush your teeth and the toothpaste foams on the teeth, the sodium lauryl sulfate is working. Foam is a natural dirt lifter, meaning it helps lift debris out of your gums and off teeth. So, it’s no wonder why many companies add it to their toothpastes.

However, this ingredient is a bit of a doubled-edged sword, as it can also cause canker sores. Sodium lauryl sulfate is a harsh chemical. Your gums and the inside of your lips are very thin and are lined with delicate mucous membranes. And when you combine a sensitive membrane and a harsh chemical, irritation can occur. The sodium lauryl sulfate acts as an irritant and, for many people, this irritation can be the cause of their canker sores.

The following cause of canker sores? It’s a bad habit that over 34 million people in the United States practice…


Certain allergies can cause canker sores. Common culprits include pine nuts (used in pesto) and certain spices. So, the next time you get a canker sore, review everything you’ve eaten to see if you can pinpoint similarities between breakouts.

A common reason is that allergies can irritate the sensitive mucous membrane on the inside of your lips and gums. When these membranes become irritated, canker sores can occur.

While many allergies are relegated to certain seasons, the following cause of canker sores can hit all year round…

Vitamin B12 Deficiency

Vitamin B12 (cobalamin) is an important vitamin that your body needs to function properly. That means a vitamin B12 deficiency can be serious, leading to problems that include the development of canker sores.

There are many reasons why a vitamin B12 deficiency causes canker sores. One of the main reasons is due to the fact that vitamin B12 plays an integral role in your body’s healing process. Specifically, when your body encounters bacteria and foreign substances that can cause harm, your immune system kicks in to keep you well.

However, if you have a vitamin B12 deficiency, the sensitive mucous membranes in your mouth can become susceptible to this immune response. As a result, canker sores may form.

The following cause of canker sores? It’s a real pain—literally…

Mouth Trauma

Any time you experience injury to the mouth, you run the risk of developing a canker sore. Examples of mouth trauma risks include a vehicular accident or sports injuries from contact sports like Lacrosse, field hockey, and baseball.

Mouth trauma causes canker sores because, at its essence, a canker sore is simply a wound that occurs inside the mouth. If you suffer mouth trauma that opens up the mucous membrane, that naturally means a canker sore can develop in that spot.

The next cause of canker sores is a milder form of trauma, and may be one that you do up to twice a day!…


Smoking in this context includes the use of tobacco products like cigarettes, e-cigarettes, pipes, and cigars. At first, smoking tobacco products may seem harmless. After all, tobacco is a natural plant. However, the truth is that tobacco is not the only substance that you inhale when you smoke. That’s right: tobacco products contain lots of harsh (and cancer-causing) chemicals and substances.

These chemicals can lead to canker sores (and many other health problems). Specifically, these chemicals can irritate the mouth’s sensitive lining, leading to mouth ulcers.

Of course, smoking in general lowers the immune system. And people with lowered immune systems are at increased risk of these ulcers.

Vigorous Tooth Brushing

It’s considered good dental hygiene to brush your teeth often and with a firm pressure. However, if you brush your teeth too vigorously, it’s all too easy to cause a canker sore.

What Exactly is Vigorous Tooth Brushing?

Vigorous tooth brushing can mean:

  • Brushing too often
  • Brushing with toothbrush bristles that are too firm
  • Brushing with an unnecessary intensity

How Vigorous Tooth Brushing Causes Canker Sores

There are several ways that vigorous tooth brushing can cause canker sores. What usually happens, though, is that the person brushes with such ferociousness that the toothbrush slips off the teeth and the vigorous stroke lands across the sensitive gum membrane. This action causes a surface laceration on the gums, which then turns into a painful canker sore.

The following foods can also lead to loss of tooth enamel and canker sores, too…

Acidic Foods

Acidic foods are those that have a high acid pH level. If you think about what kinds of foods taste sour, that is a good indication of which foods are acidic.

What are Some Acidic Foods and Drinks?

Examples of acidic foods include:

  • Lemons
  • Limes
  • Grapefruits
  • Mandarins
  • Oranges

It’s not just acidic foods that can cause canker sores, either. Beverages that are made out of acidic foods can also cause canker sores in the mouth. These drinks include:

  • Lemonade
  • Limeade
  • Iced tea

Why Acidic Foods Cause Canker Sores

The primary reason why acidic foods cause canker sores? Acid in the food or beverage irritates the sensitive mucous membrane on the gums, under the tongue, and on the inside of the lips. If there is any kind of tiny sore that has already developed, the acidic food will simply make that tiny sore worse, and it’s likely to develop into a canker sore.

The upcoming cause of canker sores? About 4 million people in the United States wear them at any given time…

Dental Braces

If you wear traditional braces, you should be aware that canker sores may become a common occurrence. We don’t say this to discourage you from wearing dental braces, as they are helpful in correcting misaligned teeth.

However, they do sometimes cause trouble for the wearer that can lead to one or more canker sores. That is one reason why it’s so critical to have regular checkups when you have braces. 

How Dental Braces Can Cause Canker Sores

Traditional metal braces have small wires that connect each brace to the adjacent tooth. Sometimes there is a loose end of the wire that can get turned inward toward the gum line. When this happens, it’s not only painful; it can also cause a canker sore in that spot.

The solution? When you visit your orthodontist, have them carefully check the wire to make sure no loose ends are turning toward the gums. Many orthodontists also give their patients clear, unscented wax to place over their braces to reduce the risk of irritating the mucous membranes in the mouth.

Hormonal Changes

Hormones regulate what’s happening in our body. Now, the body needs several different types of hormones to function properly, and at any time the levels of individual hormones fluctuate up and down as needed. When hormone fluctuations occur, lots of symptoms can develop, including canker sores.

How Hormone Changes Cause Canker Sores

Hormonal changes can upset the normal hormonal balance in the body. When these delicate levels are disrupted, canker sores may develop.

What are Common Times for Hormonal Changes?

At certain times in our lives, certain hormones become radically large in number compared to other hormones. These times include:

  • Puberty
  • Menopause
  • Pregnancy

Combat Canker Sores Now

Now that you know the most common causes of canker sores, you stand a good chance of avoiding this painful affliction altogether.

However, there are some causes that can’t be avoided (like stress), and you may end up getting one or more canker sores in your lifetime. When that does happen, don’t panic. There are a variety of remedies for canker sores, and this condition doesn’t warrant a trip to the dentist’s or doctor’s office.

Remedies for Canker Sores

You can successfully treat canker sores at home. Most of the remedies for canker sores will either help prevent them from occurring in the first place, or they will help you minimize the duration of the outbreak.


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