Canker Sores (Aphthous Ulcer)

Last Updated on: 20th May 2023, 06:36 am

About 20% of the general population has suffered from this very common affliction. The condition occurs more frequently in children and adolescents. When they reach adulthood, the frequency decreases; however, it can be extremely annoying and painful when it happens. The word thrush derives from the Greek, to a burning ulcer.   

The origin of it is still unknown and could be multifactorial. They manifest as ulcers caused by a viral infection, but in some cases, it is difficult to determine the precise cause. The purpose of this article is to expand the known information so you can differentiate them and know when to see a doctor.


What are canker sores?

canker sores
This is one of the most common diseases of the mouth and it is also known as aphthous ulcers.

This is one of the most common diseases of the mouth and it is also known as aphthous ulcers. They manifest as small, round, or oval ulcers of a white or yellow color with a  reddish contour. They generally affect the soft tissues of the mouth such as the gums, tongue, inner cheeks and lips. They are shallow and clean, that is, they do not present an infection. We usually realize that we have a canker sore when we drink acidic juice or something salty, causing great pain while eating and speaking. It usually heals on their own and then reappear in the same or another place after a period of time. 

Classification: There are three main  definitions:

  • Mild or minor: These are small ulcers, less than 10 mm in diameter. They can be circular or oval and generally affect the majority of the population. They heal in approximately one week and do not leave a scar.
  • Major or serious: Major canker sores are similar to minor ones but are a bit deeper and more destructive, with a size of 10 mm – 1 cm in diameter. They take approximately two weeks to heal, are very painful, and leave a scar when healed. They are often round and have defined borders, although they can be irregular when they are large.
  • Herpetiform or severe: herpetiform canker sores are the least common types that usually occur in the elderly. They appear as very small groups forming larger ulcers. They are more painful both when eating and speaking; they heal in approximately less than a week, without leaving a scar. 


What causes canker sores?

The exact cause has not been defined. It is not known why some people are more prone to them, but several factors  increase the probability of having them:

  • An allergic reaction, or hypersensitivity to certain foods.
  • A minor injury to the mouth from dental work, excessive tooth brushing, a sports accident, or accidental cheek biting.
  • Stress
  • Injury from braces
  • Toothpastes and mouthwashes containing sodium lauryl sulfate
  • Viral infections
  • Nutritional deficiencies
  • Lack of vitamin B-12, zinc, folate, or iron
  • Hormonal changes 
  • An allergic response to certain bacteria in the mouth
  • Helicobacter pylori, the same bacterium that causes peptic ulcers
  • Medications such as NSAIDs
  • Rubbing against teeth in poor condition; broken teeth, with sharp edges, etc., can make small wounds that lead to sores.
  • Poor oral health increases the risk of small wounds getting worse. 
  • Smoking is a risk factor,  increasing the risk of oral cancer
canker sores
Complex canker sores can appear in people with a deficient immune system.

. Complex canker sores can appear in people with a deficient immune system, including:

  • Lupus
  • Behcet disease
  • Celiac Disease 
  • Ulcerative colitis
  • crohn’s disease


What foods cause thrush?

Although it is not always due to the ingestion of food, certain foods can cause the appearance of sores in the mouth. Some of them are:

  • Nuts (especially walnuts)
  • Pineapple
  • Some cheeses
  • Spices
  • Gluten
  • Alcohol
  • Vinegar
  • Some acidic foods
  • Especially chocolate, coffee, strawberries, eggs, and spicy foods 

On the other hand, very hot, hard, or highly-seasoned foods prevent the pain from increasing.


Are canker sores contagious?

They are not contagious even if you have an open ulcer. In short, it is not communicable.

They are not contagious even if you have an open ulcer. In short, it is not communicable.  If you have a sore in your mouth and you don’t know if it’s a canker or a cold sore, take a look at where it appears: cold sores usually appear outside the mouth, around the lips, chin, or nostrils. Canker sores always appear inside the mouth. Cold sores are caused by the herpes simplex virus, making it quite contagious and easily spread. It presents as a fluid-filled blister, which makes it easily differentiated.


Symptoms of canker sores

Commonly. the following symptoms may occur:

  1. Sensations of burning or tingling in the mouth previously
  2. A red, painful lump will then form inside the mouth
  3. It will eventually leave a white, gray, or yellow open wound with a red border due to inflammation.

The diameter can be less than 1 cm.  can appear as one, several scattered, or together, forming a very large one. The most noticeable symptom is pain when talking or eating.

In severe cases, you may also experience:

  • Fever
  • Physical slowness
  • Swollen lymph nodes 


The fastest cure for canker sores

Currently, home treatments are used; they can be very effective for minor cases and in some major cases However, a different and more focused management may be required for the most severe canker sores pain. Keep in mind that it heals completely in 1-2 weeks without treatment.

Fast and easily acquired treatments are available over-the-counter to help with the symptoms. In some other cases, the patient may require a prescription.

Fast and easily acquired treatments are available over-the-counter to help with the symptoms. In some other cases, the patient may require a prescription.:

  1. Topical medications. Your doctor may prescribe a topical medication that contains a steroid for inflammation and a topical pain reliever such as lidocaine and/or anesthetics such as benzocaine for pain relief. Aftasol, a prescription ointment described as an “oral paste,” can reduce pain and healing time.
  2. Antiseptic mouthwash: While over-the-counter antiseptic mouthwash with chlorhexidine or dexamethasone is unlikely to reduce the incidence of canker sores, it may decrease pain and discomfort in the tongue. Wiater and salt rinses or water and baking soda are common. Another option is to apply a mixture of water and hydrogen peroxide to the sore with a cotton swab.
  3. Corticosteroid ointments such as fluocinonide, beclomethasone, or hydrocortisone hemisuccinate
  4. Antibiotics such as doxycycline are recommended for recurring canker sores.
  5. Oral medications. Sucralfate (Carafate) for ulcers and colchicine (Mitigare) for gout also treat canker sores. 
  6. Cauterization. Dental lasers can help you feel better right away. The doctor may also cauterize with chemicals such as debacterol or silver nitrate.
  7. Topical (gingival) hyaluronic acid: Topical hyaluronic acid is applied directly to the sore with clean hands. Hyaluronic acid acts as a barrier between the sore and the rest of the mouth. They are purchased over-the-counter (OTC) in 0.2% formulations, or stronger treatments may be prescribed by a doctor or dentist.
  8. Supplements: Some people take supplements such as arginine, vitamin C, and lysine. There is no definitive dose that can cure these sores, but researchers have used 3 to 5 grams (g) of arginine per day or 3 to 4 g of vitamin C taken for one day. People should always check with their doctor before taking any supplements to make sure they don’t interfere with other medications.


Natural treatment at home

Fresh aloe leaves and aloe gel in the cosmetic jar on wooden table.
  • The use of aloe vera in the oral area is not widespread. However, it provides many effective and natural solutions to the different conditions that develop in the mouth, including canker sores, herpes, abscesses, cracks in the lips, wounds, mouth ulcers, inflammation and irritation caused by dentures or braces, orthodontics, as well as after the extraction of a molar. It has an anti-inflammatory and cellular restorative power that helps relieve different conditions.
  • Candies to suck are very useful for children. Choose a food supplement based on hyaluronic acid and zinc with a sweetener. These candies are sold in pharmacies or parapharmacies.
  • Applying ice or small amounts of milk of magnesia to the sores can relieve pain and promote healing.
  • Rinsing your mouth with a mixture of warm water and baking soda or salt (1 teaspoon per 1/2 cup of water) also helps with pain and healing.
  • Honey has been shown to have extensive antiseptic and healing properties.


Why do I keep getting thrush?

According to studies, a family history where all members or at least the parents have had the condition can be inherited by the children. Likewise, a repeated presentation of the problem may be an alert of an association with another health problem. Your dentist should evaluate your medical history and in some cases refer you to a doctor or specialist to assess whether your immune system has been weakened or otherwise affected.

It is very important that before reaching any conclusion, you adequately review your oral hygiene, such as brushing twice a day, using dental floss, rinsing with mouthwashes, and attending dental check-ups. This will help identify if the recurrence of canker sores in your mouth is associated with gum disease, oral hygiene, or poor habits.

In extreme and not very common cases, a condition called relapsing oral aphthosis (ROA) is characterized by the recurrent appearance of painful, rounded, well-defined ulcers with an erythematous border and a yellow-grayish pseudomembranous background in the oral cavity, without an underlying disease that justifies it. The cause is unknown but it manifests between 10-19 years of age and may be persistent throughout life.


When to go to the dentist if I have canker sores?

If you are one of the people who suffer from thrush or experience the following, see your dentist:

  • With outbreaks more than three times a month, you should seek professional help from a dentist to rule out food allergies or other systemic causes.
  • Large, painful canker sores that won’t allow you to eat or drink
  • Canker sores that cause a fever or last more than two weeks

In these cases, you may be prescribed a topical medication or a special mouthwash to help reduce any discomfort.

If you have the following symptoms, you should see a doctor:

  • Eye discomfort
  • Fever
  • Eruptions
  • Sores
  • fatigue  in other parts of the body
  • aches
  • Unexplained stomach issues


Can we prevent canker sores?

We cannot prevent canker sores since the exact cause is not well defined, but we can reduce discomfort in the mouth. You are advised to brush your teeth with a soft bristle toothbrush after every meal to keep your mouth free of food that could cause discomfort. 

You are advised to brush your teeth with a soft bristle toothbrush after every meal to keep your mouth free of food that could cause discomfort.


  • Most canker sores heal on their own in a few days to a couple of weeks. While you wait for them to go away, you can take pain medication (pain relievers).
  • Avoid acidic and spicy foods, as they can cause more irritation and pain.
  • Brush your teeth and rinse your mouth with toothpaste that does not contain sodium lauryl sulfate.
  • Use mouthwash without alcohol.



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