• Mouth ulcers, also known as canker sores, aphthous ulcers or aphthous stomatitis are painful, recurrent lesions which occur on oral mucosa, especially on buccal areas where teeth or dental appliances may have caused damage.

  • They are shallow painful sores that have a shedding base with erythematous margins, may occur singly or in clusters and resolve spontaneously depending on their severity, in a week to 2 months usually with no scarring. They may recur 2 to 4 times a year or remain almost continuous.

  • Mouth ulcers affect 10 to 20% of the population and are more common in childhood to early adulthood.

  • Patient risk factors for developing an aphthous ulcer:

    • Family history
    • Female
    • Age less than 40
    • Immunodeficiency
    • Vitamin and mineral deficiencies (weak link)

  • Precipitating factors for developing an aphthous ulcer:
    • Mucosal injury
    • Stress
    • Food (eg. chocolate, coffee, peanuts, cheese, tomatoes, citrus, strawberries, nuts, alcohol, carbonated beverages)
    • Medications (eg. NSAIDs, beta-blockers, cytotoxic agents such as methotrexate)
    • Smoking cessation
    • Other chemical irritant (eg. toothpaste with sodium lauryl sulfate)
  • There is no convincing evidence of association between aphthous ulcers and premenstrual period, pregnancy or menopause.

  • For more information and photos, see:

  • One or more shallow, painful sores with a white or cream coloured coating and reddish border

  • Present on oral mucosa and at the base of the gums

  • History of recurrent episodes

  • Occasionally accompanied by fever, listlessness, swollen lymph nodes

  • Three types of canker sores:

Type Description Prognosis
Minor (80%) 
  • Occur singly or in clusters of up to five lesions
  • 2 to 10 millimetres in diameter
  • Oval in shape
  • Clearly defined outline with red and inflamed borders
  • On lips, cheeks, floor of mouth, underside of tongue, and soft palate
  • Painful
  • Resolve spontaneously in 7 to 10 days
  • Frequent recurrences possible
Major (12%)
  • Occur in clusters of 2 or more lesions
  • More than 10 millimeters in diameter
  • May be irregular in shape
  • More common in patients with compromised immune system
  • May take up to six weeks to heal
  • May cause scarring

(8 %)

  • Often in clusters of 5 - 100 small sores
  • 0.5 to 3 millimeters in diameter
  • May coalesce into an irregular shape
  • Usually develop in later life
  • Not associated with herpes virus infection
  • Heal without scarring in one to four weeks
  • May cause scarring

Rule out the following conditions which may have signs / symptoms similar to canker sores:

  • Thrush - manifested by superficial, gray to white curd-like areas on lips, buccal mucosa, tongue and/or palate, which can be scraped off to reveal an erythematous base. Removal of plaques may cause mild bleeding which helps confirm diagnosis of thrush.  Refer to Guideline for Oral Thrush.

  • Herpes simplex infections (may be HSV1 or HSV2) - multiple ulcerous or vesicular lesions initially transmitted by direct contact of saliva with another infected person. These may be recurrent and are often activated by such risk factors as: sunlight or cold exposure, respiratory infection, fever, trauma, menstruation, or if the person is immunocompromised. Refer to patient's primary care provider for antiviral therapy if needed. Refer to Guideline for Cold Sores.

  • Chicken pox (varicella) which involves presence of typical lesions on skin and mucous membranes, and spread to head, trunk and extremities. Usually occurs in children under 10 years old.

  • Shingles (Herpes zoster) - clinical diagnosis is based on vesicular eruption on one side only, often with prodromal pain which may involve sensory nerves and overlying skin of the head, trunk or limbs. Shingles are more common in adults. Refer to patient's primary care provider for diagnosis, antiviral and analgesic therapy.

  • Coxsackievirus (hand, foot and mouth disease) usually occurs in children, manifests as small (1 - 2 mm), tender lesions usually on the posterior pharynx including tonsils, soft palate, uvula and raised areas on hands and feet. No need to refer, but recommend fluids to prevent dehydration.

  • Mononucleosis which usually involves close contact with other infected persons and includes generalized swollen lymph nodes, especially in the neck and groin. Fever blisters may occur on lips. Refer to patient's primary care provider for blood tests and diagnosis.

  • Syphilis - a painless sore in the mouth or on the lips occurring 10 days to 3 months after contact with infected person. Refer to patient's primary care provider for diagnosis and antibiotic treatment.

  • Autoimmune diseases

    • Behcet's syndrome - oral ulcers >3 times/year with genital ulcers, uveitis and retinitis

    • Reiter's syndrome - concurrent uveitis, conjunctivitis, arthritis

    • Inflammatory bowel disease - concurrent recurrent bloody or mucous diarrhea

    • Systemic lupus erythematosus - typical butterfly rash, usually painless oral ulcers

    • Celiac disease - history of intolerance to gluten

  • Squamous cell carcinoma - if ulcers persist without healing. Refer to patient's primary care provider if lesions are present for over 3 weeks.

  • Drug related oral ulcers - NSAIDs, beta-blockers, cytotoxic agents such as methotrexate.

  • Stomatitis caused by radiation therapy. Refer to attending physician for treatment.

Patients with signs / symptoms typical of canker sores usually do not require further investigation, however an assessment by the patient's primary care provider should be recommended in the following situations:

  • Major aphthae (refer if any of these points):
    • Ulcers occuring on hard palate
    • Diameter grater than 10mm
    • Has persisted for >14 days
    • Quality of life impacted (pain is severe enough to hinder eating)
    • >5 ulcers present

  • Immunosuppressed (disease or drug-induced: eg. HIV)

  • Autoimmune disorder:
    • Behcet's syndrome
    • Reiter's syndrome
    • Inflammatory bowel disease
    • Systemic lupus erthematosus
    • Celiac disease

  • Recurrences more than 6 times yearly

  • History of ulcers that last >14 days, or heal with scarring

  • Systemic symptoms (fever, joint pain, ulcers or lesions on other areas of body)

  • First ulcer occuring later in life (>30 years; more likely to be a secondary cause of the ulcer, or herpetiform type)
  • Medication-induced ulcer

1.  Non-pharmacological treatment of canker sores:

  • Ensure proper fitting dentures.

  • Use softer toothbrush.

  • Avoid hard, crusty, sharp, spicy, salty, and acidic foods and beverages that may irritate and increase pain of the ulcers.

  • Avoid use of toothpaste containing sodium lauryl sulphate (SLS).

  • Aviod use of mouthwashes.
  • Avoid dehydration by drinking adequate fluids.

  • Salt winter rinses (1/2 tsp salt in 1 cup warm water) may provide some symptomatic relief.

2.  OTC drug options:

  • Silver nitrate (level 2 [mid-level] evidence) – topical antiseptic sticks which are applied to mucous membranes, only on area to be treated, 2-3 times/week for 2-3 weeks. Cautery can lead to more rapid improvement in pain, although it does not appear to speed overall healing. Lesions can be numbed with topical lidocaine prior to treatment and patients should rinse with water for several minutes after the procedure.

  • Ibuprofen or acetaminophen may ease pain.

  • Topical pastes which form a protective layer over lesion.

  • Topical formulations containing local anaesthetics such as benzocaine or lidocaine which numb painful sores.  Example: Orajel® - Topical local anaesthetics may be associated with sensitivity reactions and should be used only up to 4 times a day.

  • Combination products which contain local anaesthetics in a vehicle that forms a protective coating over sore. Examples:  Orabase with benzocaine®, Kanka®, Zilactin-B® – also caution about sensitivity reactions and maximum frequency of application four times a day.

  • Supplementing with vitamin B12, (level 2 [mid-level] evidence), vitamin B6, folic acid and/or zinc might be associated with symptom improvement.

  • Milk of magnesia and diphenhydramine allergy liquid mixed 1:1. Patient should be told to swish one teaspoonful in mouth for about one minute and then spit out. Done every 4 to 6 hours, may help to relieve pain.

3.  Prescription Drug Option:

Triamcinolone acetonide 0.1% paste (Oracort) is indicated as adjunct treatment for temporary symptomatic relief of oral inflammatory lesions or ulcerative lesions resulting from trauma.

  • It is considered to have medium range potency.  There are no published randomized trials proving efficacy, but triamcinolone 0.1% in dental paste is commonly the comparator agent in trials of newer drugs. (1)

  • Each gram of dental paste contains triamcinolone acetonide 1 mg (0.1%) in a protective emollient vehicle containing gelatin, pectin and sodium carboxymethylcellulose in a polyethylene and mineral oil gel base.

  • Dosage: Apply 0.5 cm to sore at bedtime to allow steroid contact with the sore overnight. It may be necessary to reapply 2 or 3 times a day after meals depending on the severity of symptoms.

  • Start at onset of symptoms and stop with resolution. If there is no significant healing in 7 days, refer to patient's primary care provider for re-evaluation.

  • Topically applied triamcinolone can be absorbed through the skin and mucous membranes; however the small amount of steroid absorbed when used as recommended makes any systemic effects unlikely.

  • Pregnancy - Risk Factor C: Studies on animals show adverse effect and toxicity on fetus, but there are no adequate and well controlled studies done on pregnant women. Triamcinolone should be avoided in early pregnancy and used topically only if the potential benefit outweighs the potential risk to the fetus.

  • Lactation: Topical triamcinolone has not been studied during breastfeeding. Since only extensive application of the most potent corticosteroids may cause systemic effects in the mother, it is unlikely that short-term application of topical corticosteroids would pose a risk to the breastfed infant by passage into breast milk.

Directions for use of triamcinolone oral paste:

  • Press a small dab of about 0.5cm or slightly more if needed over the sore, until a smooth, slippery, thin film develops. Use only enough to coat the area with a thin film.

  • Do not rub in, as this may cause the film to break and become granular or gritty.

  • Use at bedtime and 2 or 3 times per day after meals

  • Do not eat or drink 30 minutes after application

Assess Benefit in 7 days:

  • Refer to patient's primary care provider if:

    • ulcers have not significantly improved after 7 days treatment; or, if not resolved after 14 days.

    • sore has enlarged or more have developed

    • pain not controlled, or difficulty chewing or swallowing

    • systemic symptoms develop

  • Should be siginificant healing of the ulcer and pain reduction

  • Advise to stop if ulcer has resolved; if improved but not resolved, instruct to continue treatment for another 7 days.

Assess Adverse Effects:

  • If excessive local irritation, discontinue treatment and see patient's primary care provider - may indicate perioral dermatitis, secondary infection.

Detailed information on contraindications, cautions, adverse effects and interactions is available in individual drug monographs in the CPS (e-CPS), Lexi-Comp, AHFS, www.drugs.com or other reliable drug monograph references. For comprehensive drug comparisons, see RxFiles charts (www.rxfiles.ca).  This information should be routinely consulted before prescribing.













Anbesol Ex Strength
Anbesol Max Strength

Benzocaine 10%
Benzocaine 20%
Benzocaine 20%


Canker Care +
Canker Cover Patch

Menthol 0.5%
Menthol 2.5 mg

Aloe vera
Polyvinyl pyrrolidone Sodium hyaluronate


Cold Sore Lotion

Camphor 4%

Menthol 2%

Benzoin 10%


Fletcher’s Sore Mouth Medicine

Potassium alum 1.28%
Potassium chlorate 2.5%



Benzocaine 20%



Gelatin 13.3%

Pectin 13.3%

Sod carboxymethyl cellulose 13.3%

Gelatin 13.3%

Pectin 13.3%

Sodium carboxymethyl cellulose 13.3%


Orajel Regular
Orajel Max Strength
Oragel Mouth Sore
Oragel Ultra Canker Sore

Benzocaine 10%
Benzocaine 20%
Benzocaine 20%
Benzocaine 15%, menthol 2%

Zinc chloride 0.1 %

Gel, liquid, paste


Benzocaine 10 %

BKC 0.12%, tannic acid 6 %



Benzocaine 10 %


  • pseudoDIN: 00951092
    • Max of 4 claims per 365 days per patient

  • May prescribe sufficient quantity to treat ONE aphthous ulcer, which is usually 7 days. 
    • If patient has had significant healing, but not full resolution, after 7 days, may extend treatment to 14 days.  If one tube would not be sufficient for their treatment, a refill can be given to achieve 14 days of therapy.
    • Each new aphthous ulcer is to be treated as a distinct episode and re-assessed.

  • Only products with an official indication from Health Canada for oral aphthous ulcers and/or those recommended by reputable and reliable guidelines are considered for these guidelines.  Only the active ingredients in the "products" section are approved for pharmacist prescribing.

No part of this work may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the copyright holder. For copyright permission requests, please contact druginfo@usask.ca.

Prepared by medSask
Reviewed by Dr. D. G. Bishop, Family Physician and Loren Regier, Pharmacist, RxFiles Academic Detailing Program
Funded by the Saskatchewan College of Pharmacy Professionals
Posted May 2010. Updated May 2017