Mouth blisters what's cause n remefy?

Cold Sores. These are caused by a herpes virus. There are some treatments for thjis now, but they usually go away in a week if you treat them or 7in 7 days if you don't.
Viral infection. Herpes virus is very common. Abvreva works but is expensive. Apple cider vinegar burns like firebut seems to make them go away faster and it is cheap.