Canker Sores Treatment: Prevention Tips & Remedies

Treatment for canker sores can vary depending on their size, duration and pain intensity. The best remedy I’ve found is prevention. 

I’ve always suffered from canker sores. From the time I was a child I would get a painful sore in my mouth at least 3 times a year.
Strangely enough since I’ve moved to Italy, I have probably had a canker sore only 5 times in nearly 15 years. As soon as I return to Barbados on holidays, like clockwork I get a canker sore. I’m still not too sure why.

Before I get into what you can do to prevent them or reduce the pain once they occur, I must explain what they are.

What they are

Canker sores (aphthous ulcers or aphthous stomatitis) are small ulcers which appear on the soft tissues inside the mouth. They are usually painful and can inhibit drinking, eating and even talking.

Canker sores are not cold sores.

When people speak about cold sores they are speaking about herpetic lesions caused by Herpes Simplex Virus type 1 (HSV-1) or more rarely by Herpes Simplex Virus type 2 (HSV-2). Cold sores form on areas on the outside of the oral cavity – lips, chin, nose etc. These are contagious.

Canker sores are not contagious and have no known exact cause. Trust me as a dentist I’ve spent way too much time scouring articles trying to find out. Some individuals are more susceptible to canker sores while some seem to never have them. There seems to be a genetic component but again, there just hasn’t been enough data to determine this fact with any certainty.


In dentistry we classify them in three categories depending on their size. The most common form –minor sores  are individual sores between 3-11 mm in diameter. They are usually circular or oval shaped  ulcers  white or yellowish in color, surrounded by a red or pinkish border. They heal without any form of medical intervention between 11-14 days without any scarring.

Major sores are greater than 11 mm in diameter and the ulceration usually is much deeper. These take longer to heal. Weeks and sometimes even months. These can leave scarring on the soft tissues. You should visit your dentist with the appearance of these types of sores. 

Herpetiform sores (remember these are not caused by herpes). Herpetiform is an adjective used to describe their appearance. These are large groups of multiple sores which only reach about 3 mm in diameter. However there can be more than 50 sores clustered in one area. Once again you should seek out the assistance of a dentist if herpetiform sores occur in your mouth.

I’ve already indicated there is no known exact cause. There are however, certain factors which seem to increase their occurrence.

Potential Causes

Trauma or injury to the mouth.
For me this is number one. Even simply biting any part of the inside of the mouth seems to herald their arrival. Braces, vigorous tooth brushing, injury to the mouth from sports and of course any dental work which involves trauma to the soft tissues can cause them to appear in susceptible individuals.

Sodium Lauryl Sulfate

Toothpaste with SLS
Avoid toothpastes with SLS

If you get canker sores frequently you should look at switching out your toothpaste for one that doesn’t contain sodium lauryl sulfate. Check the ingredients in your toothpaste on the label. Sodium lauryl sulfate (SLS) is what causes the foaminess in most cosmetic products. Therefore it adds no beneficial value to the effectiveness of your toothpaste.  Some toothpastes designed for smokers do not contain it. Here are some brands which don’t contain it – Wisdom Smokers Anti Stain, Parodontax, Biorepair Plus.  Again just look at the label of your toothpaste and you can choose accordingly.

Acidic foods

Fruit concentrate with sodium benzoate
Fruit concentrates with sodium       benzoate should be avoided

Many websites indicate citrus fruits. Personally eating oranges, tangerines e.t.c have never brought on canker sores. They can for some people.  However citrus drinks made from concentrates do cause them to occur more frequently for me.
In Barbados quite a few restaurants use fruit concentrates in their juices. These juices  cause canker sores for me. There is budding research that sodium benzoate a common preservative used in food can increase the occurrence of canker sores.
Acidic foods can also include sauces such as barbecue, ketchup and mustard so you should monitor your intake of them.

Other potential causes include: food allergies/sensitivity, diets low in folic acid and B12, smoking, emotional stress, certain medical conditions e.g HIV, Chron’s disease, systemic lupus  erythematosus and particular medications.

When should you visit your dentist

In the case of minor canker sores they usually self heal within 11-14 days. These do not normally require you going to a dentist.
However If you do notice:
They are taking longer to heal than 15-20 days
They are increasing in size or their dimension is larger than usual
Irregularly shaped or spreading
You have fever or swollen lymph nodes
Extreme pain which prevents you from eating or staying hydrated

You should see your dentist who will evaluate the lesion or lesions and determine the best course of treatment especially in the case of severe pain.


When I treat patients who already have canker sores present, I try to be as gentle as possible in procedures I may be carrying out. This is because I know there is a possibility that I can cause the presence of another one if they are already present in the mouth.

Over-the-counter medications work well enough in most cases. The active ingredient is benzocaine or lidocaine in most of these products. I absolutely love the little strips that cover the actual sore and release pain medication. Other topical products meaning you rub them directly on the sore can bring instant relief but I find that unless they are in a thick gel form  they are short acting because saliva will usually wash them away quickly. My absolute favorites are Alovex gel and these covering strips. I carry these on all trips, even road trips with me.

Stay away from mouthwashes which contain alcohol as these will irritate the lesion. You can use a more soothing mouthwash of 1 teaspoon baking soda or salt to 1/2 cup lukewarm water and swish very gently in the mouth for 30 seconds. You can do this about 3 times a day.

Stay hydrated with water. You will notice that as the lesions dry out they tend to hurt more. The pinnacle of pain for me is when I’ve just woken up, so my mouth is dry. Keeping the soft tissues moist will reduce the sensation of pain.

DO NOT USE  acyclovir or other labial herpes treatments for canker sores. I hate to have to say this but I’ve see this a few times. The causes of the two conditions are completely different and acyclovir for labial herpes is not meant to be ingested.

If the pain is extremely severe for a patient I will then prescribe over the counter medications after visiting them.

Unfortunately for us canker sore sufferers avoiding them completely is the best remedy out there.  Always consult your medical doctor or health care professional before treating any medical condition.

What are your tips to prevent canker sores? What do you notice causes them?

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