Stages of canker sore

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What Are Canker Sores?

If you’ve ever had those open, shallow sores in your mouth and taken a gulp of orange juice, you know what a pain canker sores can be.

Canker sores (also known as aphthous ulcers) only happen inside the mouth. You can get them on or under the tongue and on the inside of the cheeks and lips — the parts of the mouth that can move. They usually pop up alone, but sometimes they show up in small clusters.

The good news is that they usually go away on their own without treatment.

What Are the Signs of a Canker Sore?

Your mouth might tingle or burn before a canker sore appears. Soon, a small red bump rises. Then after a day or so it bursts, leaving an open, shallow white or yellowish wound with a red border.

The sores are often painful and can be up to half an inch across, although most of them are much smaller. Aside from the annoying pain in the mouth, you’ll generally feel OK.

Canker sores are not like some other mouth sores, such as cold sores. You can’t get canker sores by sharing food or kissing someone.

If you have a sore and you’re wondering if it’s a cold sore or a canker sore, just look at where it shows up: Cold sores usually appear outside the mouth, around the lips, chin, or nostrils. Canker sores are always found inside the mouth.

Who Gets Canker Sores?

Canker sores usually begin showing up between the ages of 10 and 20, although they can happen at any time in a person’s life. They’re fairly common: About 1 in 5 people get them on a regular basis.

About twice as many women as men get them. Doctors think that may be due to the differences in male and female hormones, especially because women often get them during certain times in their menstrual cycle.

What Causes Canker Sores?

No one knows exactly what causes them. But they can run in families. That means if your parents or siblings get canker sores, the genes you share with them make it more likely that you’ll develop the sores too.

There may be a connection between canker sores and stress. If you get canker sores around exam time or some other big event in your life, it may be a sign of how much stress you’re under.

Mouth injuries (like biting the inside of the lip or even brushing too hard and damaging the delicate lining inside the mouth) also seem to bring on canker sores. Sodium lauryl sulfate (SLS), an ingredient in many toothpastes and mouthwashes, has been linked to canker sores, and sometimes the sores can be a sign of an immune system problem.

Finally, not getting the right nutrition (such as not getting enough iron or vitamin B12) also might contribute to some cases of canker sores.

How Are Canker Sores Diagnosed?

Canker sores are fairly common, but that doesn’t mean they should be ignored. If you have sores that last longer than 2 weeks or you can’t eat or drink because of the pain, call your doctor. Also call if you get the sores more than two or three times a year.

Usually, no tests are needed to diagnose canker sores. Your doctor can identify them based on your medical history and physical exam alone.

In some cases, doctors may want to do blood tests to find out if another condition — like a vitamin deficiency, a problem with your immune system, or even a food allergy — could be contributing to the sores.

How Are Canker Sores Treated?

Most canker sores will heal on their own in a few days to a couple of weeks. While you’re waiting for them to disappear, you can take an over-the-counter pain reliever like ibuprofen or acetaminophen for the pain.

You’ll also want to watch what you eat. Spicy foods and acidic foods such as lemons or tomatoes can be extremely painful on these open wounds. Stay away from hard, scratchy, or crunchy foods like nuts, toast, pretzels, or potato chips for a while. They can poke or rub the sore.

Be careful when you brush your teeth. Brush and rinse with toothpastes and mouthwashes that don’t contain SLS. And avoid brushing the sore itself with a toothbrush, which will make it worse.

If you have canker sores that do not get better after a few weeks, if the sores keep coming back, or if they make you feel so sick that you don’t want to eat, call your doctor or dentist. He or she may prescribe a topical medicine or special mouthwash to help heal the sores.

For medicines that are applied directly to the sore, first blot the area dry with a tissue. Use a cotton swab to apply a small amount of the medicine, and don’t eat or drink for at least 30 minutes to make sure it isn’t washed away.

They can certainly be a pain, but in most cases canker sores aren’t serious and should go away on their own.

Reviewed by: Patricia Solo-Josephson, MD Date reviewed: June 2017

Man with mouth ulcers.

A common type of mouth sore is an ulcer. Mouth ulcers can be caused or triggered by:

  • stress or anxiety hormonal changes
  • any injury or damage to the mouth, such as from sharp teeth, dentures, or braces
  • a reaction to certain foods, drugs or toothpastes
  • some infections and diseases
  • certain medications and medical treatments
  • vitamin deficiencies.

Mouth ulcers are usually round and white/pink in colour and usually occur inside the lips, inside the cheeks, on the bottom of the mouth or under the surface of the tongue.

Mouth sores will usually only last a couple of weeks, especially if treated. However, if your mouth sores last longer than this, it may be a sign of a more serious problem.

Check your symptoms with healthdirect’s Symptom Checker to get advice on when to seek medical attention.

Looking after yourself

It’s important to treat mouth ulcers properly to help the healing process. If after following this advice they do not get better, contact your doctor.

  • Try not to touch the sore area. Not only will this disturb the healing process but it could also cause an infection to spread. If you do need to touch the area, make sure you wash your hands before and after.
  • Use a soft toothbrush to clean your teeth. If your sores are so painful that you can’t brush your teeth, use a mouthwash containing chlorhexidine instead. This should be available from your local pharmacy and some supermarkets. Avoid using mouthwashes that contain alcohol.
  • Salt water may help. Mix one teaspoon of salt into a cup of water, then take a mouthful of the liquid and hold it in your mouth so it covers the affected area for two minutes, then spit it out. Do not swallow it. Repeat four times a day.
  • Avoid hard foods that could rub against your mouth sore. You should also try to avoid chocolate, coffee, peanuts, almonds, strawberries, cheese and any salty foods because they may make mouth sores worse.
  • Avoid overly hot foods and drinks.
  • Drinking cool water can help to ease a painful mouth.
  • If your mouth is really sore, drinking through a straw can help.
  • Eat well. Choose fruit and vegetables that have a high vitamin C content and whole grain foods that are high in vitamin B. Seafood and iron rich foods, such as leafy green vegetables, are also recommended.
  • You can soothe any pain or discomfort with anaesthetic lozenges you can get from your local pharmacy. There are also treatments designed for mouth ulcers, but remember to always speak to a pharmacist before buying anything.
  • If you are in pain, get advice on pain relief medicines you can take.

All About Canker Sores

What Is It?
Canker sores are painful, round mouth sores. They show up in several places:

  • On the inside of the lips
  • Inside the cheeks
  • On the tongue
  • At the base of the gums
  • On the roof of the mouth (palate)

Canker sores often run in families. They also are linked with other diseases, including Behcet’s syndrome. You may have only one canker sore at a time, or many of them all at once. Most people get one, two or three sores at a time. But some people have 10 or more at a time. People who get canker sores typically have them a few times each year. Canker sores are not contagious.

Scientists don’t know what causes canker sores. Most believe that there is a problem with the body’s immune system. Emotional stress, menstruation or injury to the mouth are common triggers for simple canker sores. Certain foods such as citrus or acidic foods may trigger a canker sore or make one more uncomfortable.

Other conditions cause similar sores:

  • Blood and immune system diseases, including HIV
  • Vitamin and mineral deficiencies
  • Allergies
  • Trauma
  • Crohn’s disease
  • Lupus

Canker sores are often confused with cold sores. Cold sores are caused by a virus.

About half of the population get canker sores. Smaller canker sores usually heal within a couple of weeks and do not leave scars. For most people, they are just annoying. But some people get larger canker sores (almost one-half inch across or larger). These take longer to heal. They can be painful, and may leave scars. These sores may be so uncomfortable that it is sometimes hard to eat or speak.

You may feel a burning or tingling on your inner cheek, lip or tongue before a sore starts. Each sore takes two to three days to form. The sores are round and shallow.

Usually, you do not need to visit a doctor for your canker sores, unless it is the first time you have them. If your sores become worse over time, or start showing up more often, see your physician or dentist. He or she can do some tests for blood diseases, connective tissue diseases, drug reactions and skin disorders.

Sometimes a biopsy is needed to make sure the mouth sore is not a different disease. In a biopsy, the area is numbed and a small piece of tissue is removed. Then it is examined in a laboratory.

Expected Duration
Canker sores are painful for 3 to 10 days. Most go away after 2 weeks.

There is no way to prevent canker sores.

Only the symptomms of canker sores can be treated. Treatment is meant to make you feel better until the sores heal. Treatment cannot stop you from having canker sores again.

To reduce discomfort, you can:

  • Eat bland foods
  • Rinse with warm water
  • Use pain-relieving gels or creams on the sores

People with larger or very painful sores may need steroid medicines. These are gels or creams that are placed on the sores. They make the sores heal faster. They also keep the sores from growing.

Other possible treatments include injected steroids. There are also a few medicines you can take by mouth, but this is for the most serious cases.

When To Call a Professional
You should visit your dentist or physician if:

  • You are having sores for the first time
  • Your sores are larger than 1centimeter (almost one-half inch) across
  • You get more sores now than you used to
  • You get sores more often than you used to
  • You have other symptoms with your sores, such as:
    • Rashes
    • Joint pain
    • Fever
    • Diarrhea

Most canker sores clear up without treatment and do not leave scars. In more severe cases, medicines often help to speed up healing.

Additional Info

American Academy of Oral Medicine
P.O. Box 2016
Edmonds, WA 98020-9516
Phone: 425-778-6162

American Academy of Family Physicians
Consumer Information Site
11400 Tomahawk Creek Parkway
Leawood, KS 66211-2680
Toll-Free: 1-800-274-2237
Email: [email protected]

Canker Sores – Treatment

As with all disorders of the mouth, an accurate diagnosis by a trained healthcare professional is required before treatment is started.

As with all disorders of the mouth, an accurate diagnosis by a trained healthcare professional is required before treatment is started. This is particularly important for canker sores (recurrent aphthous stomatitis / RAS / aphthae), since several other conditions can cause ulcers in the mouth that may mimic typical canker sores.

Some conditions that can mimic canker sores include traumatic injury, autoimmune conditions, viral infections (such as herpes simplex and herpes zoster ), and most importantly, oral cancer. In addition, oral ulcers can be associated with a number of systemic conditions in which the oral ulcers represent only a small part of the underlying problem. A general rule of thumb recommended by health care professionals is that any ulcer that lasts for more than 10 to 14 days should be evaluated by a dentist and biopsied if necessary. Professionals trained in Oral Medicine have expertise in the diagnosis of such lesions.

The discomfort and severity of canker sores can roughly be categorized as mild, moderate, or severe. Mild disease is characterized by its infrequent occurrence, short duration, and lack of severe symptoms. Fortunately, most patients who experience canker sores experience mild disease (see right). While there is no formal classification to distinguish between moderate and severe disease, the presence of four or more canker sores per year with annoying but non-debilitating symptoms can be classified as moderate disease. Severe canker sores are often more widespread, more painful, and interfere with the patient’s ability to eat and speak. Unfortunately, individuals with severe disease often suffer frequent to constant recurrence.

In general the goals of treatment are threefold: to decrease pain, speed healing, and prevent recurrence. Currently, no available therapy meets all these goals, although most therapies do provide some benefit to those affected.

A large number of therapeutic agents are available, including both prescription and over-the-counter (OTC) preparations. The mode of administration can be topical, systemic, or a combination of both. The method selected depends upon the site of the lesion(s), accessibility for treatment, severity, duration, and success with previous treatment regimens.

Below is a brief discussion of the many choices available for the treatment of canker sores. These agents may relieve pain or reduce the inflammation that causes the lesion. Before using any agent it is recommended that you consult your dentist. If needed, an expert in Oral Medicine may be consulted concerning the need and feasibility of more advanced treatment protocols.

OTC preparations for treatment of RAS fall roughly into four categories: occlusives, anesthetics, cleansing agents / antiseptics, and other. OTC products often combine multiple categories in order to increase effectiveness.

Occlusives or emollients are protective coatings that block irritation of the ulcer and associated nerve endings by providing a surface covering that shields the site from mechanical irritation; stimulation from acidic, salty, or spicy foods; and temperature changes. These coating agents are pharmacologically inert substances. They generally provide relief as long as they are in place, but it can be difficult to keep them adherent for sustained periods. When protective coatings are combined with a therapeutic agent, a two-fold benefit is obtained. The occlusive prevents external stimulation of the wound site and also holds the therapeutic agent in place. Representative products in this category include Zilactin® and Zilactin®-B, Orabase®, and Orabase® Soothe-N-Seal™.

Anesthetics provide symptomatic relief and are often combined with other agents. The most frequently used agent is benzocaine 5 – 20%. However, benzocaine is a known allergen and should not be used by patients with hypersensitivity. Many OTC anesthetic products are available.

Cleansing agents/ Antiseptics can cleanse the area and decrease the number of bacteria on the ulcer surface. Products that release oxygen can be used as cleansing agents. The foaming of the oxygen exerts a mechanical action that loosens debris and cleanses the wound. Products in this category include Amosan®, Cankaid®, Gly-Oxide®, Orajel®, and Peroxyl®. Hydrogen peroxide when obtained as a 3% solution should be diluted with equal amounts of water before application either directly to the ulcer or as a mouthrinse. Sodium bicarbonate, either as a solution (½ to 1 teaspoon in 4 ounces of water) or as a paste, can also be used to for wound cleansing.

Other Approaches include the use of mild cautery or caustics to deaden nerve endings and decrease symptoms. All OTC agents in this category are mild. An available OTC product is ORA5. A professionally applied or prescribed product Debacterol® is also available for nerve deadening.

Professional care is recommended for moderate to severe lesions. Individuals with advanced training in Oral Medicine have additional expertise in managing more severe cases. In many instances, topical therapy with a potent corticosterioid may be prescribed to reduce the immune response in the area. Finally, in some cases the use of systemic corticosteroids or other immunosuppressive drugs may be warranted.

Final Cautionary Note: Because canker sores can be caused by systemic abnormalities and also be confused with other pathologic conditions that present as ulcers, it is important to seek professional attention if lesions do not resolve within two weeks.


Q: Do OTC agents work?
A: Many patients obtain some relief using these agents. Use of OTC agents is intended for mild to moderate disease. Since 1972, the Food and Drug Administration (FDA) requires that all new OTC agents must be safe and effective.

Q: It seems like I always have canker sores. Is there any help for me?
A: Individuals who have frequent canker sores should seek professional assistance from a dentist and/or be referred to an expert in Oral Medicine. The assessment of your particular situation may be extensive and necessitate consultation with other health care professionals. For example, your dentist may order dietary surveys and blood tests to help rule out the presence of food sensitivities or other systemic causes. Prescription medications may be necessary to best manage your disease.

Q: Can canker sores be caused by an allergy?
A: Yes. However, identifying the particular allergen can be challenging. This is an area where the individual patient can contribute to his or her care. Strategies for identifying potential allergens include observing any relationship between the intake of a particular food or beverages and development of canker sores. Many individuals are intolerant of wheat products (gluten), nuts, tomatoes, and various fruits. Two frequent food additives that are associated with canker sores are the spice cinnamon and benzoic acid (a common preservative found in foods and soft drinks). A trial elimination of a suspected food substance or additive is a sound approach to identifying potential allergens.

Q: Can I use a mouthrinse to prevent canker sores?
A: While not specifically marketed to treat canker sores, the regular use of Listerine® (OTC) and Peridex® or Periogard® (Rx chlorhexidine gluconate) may lessen the pain of canker sores. However these rinses often do not prevent recurrence.

Prepared by the AAOM Web Writing Group
Updated 31 December 2007

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The information contained in this monograph is for educational purposes only. This information is not a substitute for professional medical advice, diagnosis, or treatment. If you have or suspect you may have a health concern, consult your professional health care provider. Reliance on any information provided in this monograph is solely at your own risk.

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