Are canker sores (aphthous ulcers) contagious?

No, canker sores, also known as aphthous ulcers, are not contagious. Canker sores differ from cold sores (which are caused by the herpes simplex virus) in that they are not caused by a viral infection and cannot be transmitted from one person to another. Canker sores typically appear on the soft tissues inside the mouth, such as the inside of the cheeks or lips, under the tongue, or on the soft palate, and are characterized by a white or yellow center with a distinct red border [2].

What are canker sores?

Canker sores are small, painful ulcers that form inside the mouth. They can be round or oval in shape and often have a gray or white center surrounded by a red border. These sores may cause difficulty eating and speaking due to pain [1]. There are three main types of canker sores:

• Minor canker sores: These are the most common; they are small, oval-shaped, and have a red border. They usually heal within one to two weeks and do not leave scars [2].
• Major canker sores: These are less common, larger, and deeper than minor canker sores. They may be round with defined borders or have irregular edges when large. They can be very painful, take up to six weeks to heal, and may leave scars [2].
• Herpetiform canker sores: These are not common and are not caused by the herpes virus infection. They are very small and often appear in clusters ranging from 10 to 100 sores, which may merge to form one large ulcer. They typically heal within one to two weeks and do not leave scars [2].

Common causes of canker sores

The exact cause of canker sores is not entirely clear, but several factors are believed to contribute to their appearance. Potential triggers include:

• Mouth injuries: Such as accidental cheek biting, brushing teeth too vigorously, or injuries from dental work [2].
• Food sensitivities: Certain foods such as chocolate, eggs, nuts, and spicy or acidic foods may trigger the appearance of sores [2].
• Vitamin and mineral deficiencies: Low levels of vitamin B12, zinc, folic acid, or iron in the body may be a factor [2].
• Hormonal changes: Especially during the menstrual cycle in women [2].
• Emotional stress: Stress can be a trigger for the appearance of canker sores [1].
• Certain toothpastes and mouthwashes: Those containing Sodium Lauryl Sulfate [2].
• Certain medical conditions: Such as celiac disease, inflammatory bowel disease, or a weakened immune system [2].

Home and medical treatments

In most cases, canker sores disappear on their own within one to two weeks [2]. The primary goal of treatment is to relieve symptoms and accelerate healing. Some home and medical treatments can help:

• Avoid irritating foods: Steer clear of spicy, acidic, and crunchy foods that may further irritate the sore [1].
• Good oral hygiene: Use a soft-bristled toothbrush and brush gently after meals, in addition to using dental floss daily. Avoid toothpastes and mouthwashes that contain Sodium Lauryl Sulfate [2].
• Topical ointments and creams: Some over-the-counter ointments or creams can help relieve pain and protect the sore [1]. A doctor may also prescribe stronger topical medications or special mouthwashes [3].
• Pain relievers: Over-the-counter pain medications can help relieve discomfort [3].
• Natural remedies: Certain treatments, such as rinsing the mouth with salt water or a baking soda solution, can help relieve symptoms.

When should you consult a doctor?

Although most canker sores disappear on their own, you should see your doctor or dentist if you experience any of the following symptoms [2]:

• Large or deep mouth sores.
• Sores that do not heal or persist for more than two weeks [2].
• Appearance of new sores before the old ones have healed.
• Severe pain that cannot be controlled [2].
• Difficulty eating or drinking due to the sores.
• High temperature (fever) accompanying the canker sores [2].
• Sores spreading to the lips [2].

For more information on causes and treatments, you can visit Recurrent Canker Sores: Common Causes and Home/Medical Treatments (Arabic).

Medical references

• Canker Sores
• Canker Sore
• Canker Sores