Canker sores, or small ulcers within the mouth, are painful lesions that can cause your gums to bleed. They can form on your gums or elsewhere in the soft tissue of your mouth. You may feel burning or tingling at the spot of the canker sore a few days before it actually forms.

Are canker sores supposed to bleed?

Canker Sore Symptoms

The sores bleed easily (when brushing the teeth) and usually last for several days. Occasionally, they may last for one to two weeks before disappearing. Viral infections that cause canker sores may also be accompanied by a fever.

Why do canker sores bleed?

Most oral blood blisters develop following trauma to the mouth, such as biting your cheek, burning your mouth with hot food, or puncturing soft tissue with sharp food, like a chip. In the case of trauma, a blood blister usually develops quickly after the damage takes place.