​Canker Sore


Canker sores are shallow ulcers that develop in the soft tissues in the mouth or the base of your gums. They usually begin as very small, white or yellow ulcers surrounded by redness that may increase up to half an inch in size. Canker sores can be very painful, making it difficult to eat and talk. The exact cause that triggers canker sore is unknown though doctors believe a number of factors can result in this disorder include:

  • A mouth injury due to some dental work, sports injury, aggressive brushing or ill-fitting dentures

  • Certain foods including citrus and acidic fruits/vegetables

  • A diet lacking in vitamin B-12, zinc, folic acid or iron

  • An allergy in the mouth

  • Hormonal shift during menstruation

  • A disease of the immune system

  • Emotional stress

Anybody can get canker sores but you are at a greater risk if you are a female, a teenager or young adult, or have a family history of canker sores.


There are different types of canker sores each exhibiting different symptoms.

Minor canker sores:

  • Are usually very common

  • Are usually small in size

  • Are oval in shape with red edges

  • Heal within a week or two

  • Leave behind no scar

Major canker sores:

  • Are larger and deeper than minor canker sores

  • Are usually circular in shape with distinct borders

  • Can be extremely painful

  • Heal within six weeks or more

  • Leave behind excessive scarring

Herpetiform canker sores:

  • Are usually uncommon

  • Are pinpoint sized

  • Occur in clusters of tens or hundreds, merging to form a large ulcer at times

  • Have irregular edges

  • Heal within a week or two

  • Leave behind no scar

Consult our skilled doctors at the Teeth and Skin Service Line at The Aga Khan University Hospital if you experience large canker sores that are recurring or persist for long. Seek immediate medical attention if the pain is severe and uncontrollable causing difficulty in eating or drinking. A fever that may accompany the sores is alarming and you should immediately visit your doctor.

Your time with your doctor maybe limited, so make sure to prepare for your visit beforehand. Here are some tips to help get you started.

Your doctor or dentist can identify canker sores without any particular tests, from their appearance and location.

No particular treatment is necessary for minor canker sores as they tend to resolve in a week or two on their own.

In cases of painful, large or persistent canker sores, you may require medical help. Once your diagnosis has been made, the internationally trained doctors working with the Teeth and Skin Service Line at The Aga Khan University Hospital will guide you thoroughly and effectively.  Your treatment options will include:

  • Mouth rinse containing the steroid dexamethasone to ease pain and inflammation

  • Topical products including creams, gels, pastes or liquids, to be applied to individual sores, in order to reduce pain and promote healing

  • Oral medications as a last resort to treat severe canker sore. These are generally not preferable due to serious side effects

  • Need to properly investigate to rule out any other systemic illness

The Aga Khan University Hospital offers various support services to help with managing or recovering from the disease or condition. These include but are not limited to nutrition, physiotherapy, rehabilitation, specialized clinics and some patient support groups. Your doctor or nurse will advise you accordingly.

The Aga Khan University Hospital offers financial assistance to those who are in need and fulfil the eligibility criteria. For further information, you can contact the Patient Welfare Department. You can find the contact number of the Patient Welfare Department in the ‘Important Numbers’ section on the website homepage.

The financial counselling staff is available during office hours, at the main PBSD (Patient Business Services Department), to answer your financial queries on treatments’ costs and authorize admissions on partial deposit as per hospital policies allow. The financial counsellor in the emergency room is open 24/7. You can find the contact number of the Patient Business Services in the ‘Important Numbers’ section on the website homepage.

Your doctor and or nurse will give you specific instructions about the prescribed medication. Please ensure that you take or use the prescribed medicine as advised. It can be dangerous to your health if you self-prescribe. Please inform the doctor or nurse beforehand if you have experienced any adverse reactions to any medications in the past. If you experience any symptoms of drug poisoning, overdose or severe reaction please contact the Pharmacy Service at The Aga Khan University Hospital immediately. You can find the contact number of the Pharmacy Services in the ‘Important Numbers’ section on the website homepage



The information provided on our website is for educational purposes and not intended to be a substitute for medical advice, diagnosis or treatment. You should always seek the advice of your doctor or other healthcare professional provider.