This is Dr Basu, experienced Internal Medicine Specialist.
I am here to address your concerns and provide great service.
I understand your concerns.
Since antibiotics help, this still can be a bacterial infection.
However, this can be herpes simplex virus infection as well.
Another possibility can be autoimmune disorder like Behcet's disease.
Immune system can attack the oral mucosa for unknown reasons.
Cancer is not likely since the lesion is usually one or two, and painless not like blisters.
The diagnosis can be confirmed by a blister biopsy and also sending out herpes culture.
You should see a dermatologist for these tests.
This is fully treatable.
Do not worry.
It was my pleasure to help you today.
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