Question: what causes sores in the back of your mouth?
Answer: Canker Sores No one knows what causes these small, painful blisters inside your mouth. Triggers include hypersensitivity, infection, hormones, stress, and not getting enough of some vitamins. Also called aphthous ulcers, canker sores can show up on the tongue, cheek, even your gums. They usually last a week or two.