Aphthous stomatitis (canker sores) – Causes, Treatment & Prevention

What are canker sores?

Canker sores are small, painful ulcers and bubbles in the mucosa of the oral cavity or the inside of the lips.

The medical name of this condition is aphthous stomatitis.

Canker sores or ulcers in the oral cavity can be classified as:

Small – they are small, round or oval and not very painful. They appear pale yellow, and around them, the lining is usually red and swollen. They can be single or multiple. After healing, they do not leave any scars.

Large – they can reach 1 cm in diameter or more, deeper and, after healing, can leave a scar. This type of canker sores is often painful.

Herpetiform – they are small and numerous, about 1-2 mm in diameter. Sometimes some small ulcers merge into one, forming an irregular shape.

The oral ulcers (aphthae, canker sores) are a very common problem in younger children and relatively rare problem in elder people.

They often form in young people having a hereditary predisposition for their appearance. Some factors such as stress, physical or chemical trauma, food susceptibility, infections can also play a major role for the appearance of canker sores.

Canker sore

Oral treatment in the oral cavity may include antibiotics, anti-inflammatory, immunomodulatory, symptomatic, and alternative treatment options.


There are various reasons for the appearance of mouth ulcers.

The most common ones are related to stress and anxiety. People are prone to mouth ulcers when they are under a period of prolonged stress. Long stress periods lead to suppressed immune system.

Oral trauma (over brushing teeth, wearing braces, tongue, and lip biting chewing hard foods, hot foods or beverages) is usually caused by some sort of mechanic injury.

Who can be affected by canker sores?

Most people have canker sores at least once in their life span, as they most often occur in women and children.

In most cases, ulcers are caused by infection. The condition is not transmitted from person to person e.g. by kissing or using the same cutlery.

Biting, dental floss or toothbrushes can also be the cause for the appearance of canker sores.

Usually, sores are caused by injury to the lining of the mouth – by biting during feeding, sharp objects or solid foods.

Therefore, most of the canker sores affect young children, because they often put various objects in their mouths which are often dirty.

Adults having canker sores on their cheeks and their tongues are usually the result of bites during eating, sharp edges of their teeth or dental sealants. Other reasons include too strong pressure while brushing or toothbrushes with very stiff hairs that can bruise the delicate mucosa.

Why have children have canker sores more often than adults?

Canker sores are common sores that appear on the child’s tongue or mouth lining, because they tend to explore the world while putting everything in their mouths.

Aphthous ulcers
Two mid-size (approx. 3mm in diameter) aphthous ulcers on lower lip. Medical name: stomatitis aphthosa.
Source: https://commons.wikimedia.org

Biting, chewing hard, rough and sharp objects often results in injury to the soft tissues in the mouth.

As a result, small wounds are formed which are easily infected by the bacteria and lead to canker sores. Other causes include low immunity i.e. after being on antibiotic treatment.

Why have women more canker sores than men?

Some women get canker sores during their menstrual cycle. This is caused by the sudden change in hormone levels during this period.


Quitting cigarettes

When you stop smoking, canker sores may appear more often than usual. At this point your body adapts to the abrupt chemical change. This is a normal reaction, which will adjust over time. Canker sores should disappear completely within 3 weeks.


If canker sores are not as a result of a specific disease or medication, they could be often associated with an allergy to certain foods. A recent study found that food allergy is the most common reason why people have mouth ulcers.

Restricting certain foods leads to an improvement in almost all cases. Another study proved that a gluten-free diet can lead to complete remission or significant improvement in patients with celiac disease (a serious genetic autoimmune disorder where the ingestion of gluten is contraindicated) that regularly have ulcers.

Vitamin deficiency or certain diseases

The absence of certain substances also has an impact on the canker sores. Recently, more than 300 people suffering from ulcers are subjected to a study, which found that 14.2% of them has severe iron, folate and/or vitamin B12 deficiency.

After they started taking food supplements, there was a noticeable improvement in the participants. You should consult with a specialist who could determine whether the occurrence of ulcers is due to an allergy or the lack of certain substances.

Improper toothpaste choices

The cleaning compound called sodium lauryl sulfate, which is found in many toothpastes labels, is often the cause of mouth ulcers. Researchers found that families who use toothpaste with the presence of sodium lauryl sulfate, suffer more often from ulcers.


Antibiotics, like any other medication, have side effects. Note that some of them may cause the occurrence of ulcers.

Chemotherapy and radiotherapy in cancer patients

Chemotherapy and radiation therapy’ common side effect is the appearance of multiple sores – they are the most common side effect.


Mouth sores can be caused by adverse reaction to medication you are taking. Here are some such drugs.

Nonsteroidal anti-inflammatory drugs: Painkillers such as ibuprofen and aspirin.

Beta-blockers – used to treat various heart conditions such as angina, heart failure, high blood pressure and heart rhythm disturbances.

You may notice the appearance of sores in the mouth when you start taking your medicine or when increasing the dose. This, in most cases, is only a temporary side effect of the drug.

 Again, stress

Recent studies have shown that people prone to anxiety suffer more often from sores in the mouth than the more relaxed among us. After undergoing the therapy by relaxation and visualization these patients showed significant improvement in their overall condition.


Canker sore treatment can be performed by using over-the-counter medicines, which do not require a prescription from a doctor, and by applying alternative remedies, which are usually available in your kitchen.

Natural products for topical application

Honey and turmeric

For fast healing of canker sores mix 1 teaspoon of honey with 1/4 teaspoon of turmeric powder and apply the mixture to the lesions. At the beginning, you may experience burning, but the sensation will quickly disappear.

Aloe vera

Rinsing the mouth several times a day with aloe vera juice or applying aloe gel to the canker sore three times a day helps to restore tissues faster and reduces inflammation. [1]

Aloe Vera Powder and Aloe Gel: The combination of aloe and powdered gel can also be used to treat mouth ulcers. Mix 1 teaspoon of aloe vera gel with a pinch of powder and apply the mixture directly to the canker sore.

Tea tree oil

10 drops of tea tree oil are diluted in 1/3 cup of water and mixed well. Rinse mouth with the solution. This mixture has antiseptic action, helps to heal the canker sores and prevents secondary infection. Note, that the mixture should not be swallowed! [2]

A Tea Bag

Placing a bag of tea on the canker sore provides with a rich amount of tannins. It would be even better if you use herbal tea i.e. St. John’s Wort, eucalyptus, mint, sweet root, raspberries, sage.


Garlic acts as a natural antibiotic and immunostimulant. It is recommended to take three cloves, three times a day, before a meal, and it is recommended that they are finely chopped and held briefly in the mouth.


Propolis [4] is a bee product used in the therapy of various inflammatory conditions and lesions. Studies show that propolis significantly accelerates healing and prevents the reappearance of mouth ulcers.

It is also convenient to chew natural propolis.
Propolis tinctures, lozenges, and oral sprays can be used to treat conditions including canker sores, sore throats, superficial burns, inflammations, ulcers, and viral diseases.

Himalayan salt

An aqueous solution of a Himalayan salt can be used to rinse the oral cavity. In addition to aiding the healing process, a Himalayan salt is an excellent tool for maintaining oral hygiene.

Typical for the canker sores (usually gray or white colored sores, surrounded by an area of inflammation) is that they are round shaped, usually darker than the normal mouth lining (the mucous membrane lining the inside of the mouth) and extremely painful to touch.

While having canker sores you may experience tingling and mild burning even without touching them. Many pieces of research prove that ulcers in the mouth are appearing more frequently when the body is subject to physical or mental stress when the immune system is low.

Usually, canker sores affect the inside of the mouth only. They can also appear on the tongue or the insides of the cheeks, lips or throat.

If you often have canker sores although you keep good oral hygiene, you should visit your doctor because their occurrence could be a symptom of another more serious illness.

According to a study, conducted by NCBI (The National Center for Biotechnology Information) among 1000 participants, it is estimated that:

„ The lifetime prevalence of RAU(recurrent aphthous ulceration ) experience was 28.2% (n=282). It was highly significantly more common among females (31.76%).”

The research also informs about the considerably lower rate of people with mouth ulcers among smokers (12.22%) compared to non-smoker (30%).[3]

The number of mouth ulcers at a time usually does not exceed 3-4. The evolution of individual aphthae lasts about 6-7 days and, luckily, leaves no scar.

Is it necessary to visit a doctor or a dentist?

Usually, small canker sores can be unpleasant and painful, but they are not a serious illness requiring medical intervention.

Sometimes, though, very rarely, aphthae can get infected. You may experience swelling, redness and fever. If so, it is advisable to go to a doctor or dentist. Antibiotic treatment may be required.

You should not forget that not all wounds in the oral cavity are canker sores. Sometimes they are an accompanying symptom of another disease. So, in case you have noticed something similar to canker sores in your mouth cavity that does not heal within 10-14 days, it is best to consult a specialist.


  1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3491322/
    Evaluation of the therapeutic effects of Aloe vera gel on minor recurrent aphthous stomatitis
  2. https://nccih.nih.gov/health/tea/treeoil.htm
    Tea Tree Oil
  3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3892221/
    Prevalence of recurrent aphthous ulceration experience in patients attending Piramird dental speciality in Sulaimani City
  4. https://medlineplus.gov/druginfo/natural/390.html

About the author

Monika Hristova

Monika is the Editor-in-Chief at SkinPractice. She is a skin care addict and researcher, who feels strongly about helping people with different dermatology conditions from alopecia to warts.

You can read her recommendations and advice both here at SkinPractice or at Quora where she answers skincare-related questions frequently and is the most viewed author in the Skincare category with more than 3 million views or follow her on LinkedIn.

She is also a certified skin care specialist with certification from the Medical College in Sofia.

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