A canker sore is an open and sore mouth ulcer. It is the most common form of mouth ulcer and can also form within the lips or cheeks. The sores are typically white or yellow and enclosed by reddened, inflamed soft tissue.
A canker sore generally heals within 1-3 weeks without requiring treatment but the pain settles in 7-10 days. Serious cases might take up to 6 weeks to fully heal. It is recommended to seek medical care if the individual could not eat or drink or the sore has not healed within 3 weeks.
Indications of a canker sore

- Small-sized, white or yellowish oval-shaped ulcer in the mouth
- Tingling sensation in the mouth
- Sore reddened area in the mouth
In some instances, other symptoms might also arise such as:
- Fever
- Swollen lymph nodes
- Not feeling well
A doctor must be seen if a canker sore does not heal on its own within 3 weeks since this might be an indication of a mouth ulcer.
Causes and risk factors
The risk for developing canker sores is increased if the individual has a family history. Other various causes include:
- Stress
- Food allergy
- Viral infection
- Hormonal fluctuations
- Mouth injuries
- Menstrual cycle
- Immune system issues
- Vitamin or mineral deficiency
Being deficient in certain vitamins such as B3 (niacin), B12 (cobalamin) or B9 (folic acid) puts one at higher risk for developing sores. Deficiencies in iron, zinc or calcium can also trigger or worsen the sores.
Management
A canker sore usually heals without requiring treatment. Nevertheless, lifestyle changes can be done such as:
- Regularly brush and then floss the teeth to reduce the risk for a bacterial infection
- Spicy foods must be avoided to hasten the healing
- Milk, yogurt or ice cream can be consumed to reduce the pain
In some cases where the pain is severe, the discomfort can be reduced by gargling on mouthwash or salt water. It is uncomfortable initially, but can help reduce the pain.
Some ingredients present in over-the-counter topical products can help alleviate and promote healing of the sores such as:
- Benzocaine
- Fluocinonide
- Hydrogen peroxide
If a doctor or dentist is consulted, the following might be prescribed:
- Antimicrobial mouth rinse
- Antibiotic such as pills or mouthwashes that contain doxycycline
- Prescription mouthwash that contains lidocaine or dexamethasone for pain and inflammation
- Corticosteroid ointment