A gum blister is an infection in the form of an abscess that appears as a bubble on the gum and may be associated with pus drainage. There are many causes of gum blisters and something as simple as a mild accidental scraping of the gum with an object could cause a blister. However, repeated gum blisters could be a sign of a problem that is more serious.
A fistula is a recurring blister on a gum and is often caused by an infection from a tooth. Antibiotics may be prescribed to help settle the blister but this is a temporary measure since the infection remains present in the tooth itself which is causing the blister. It should be noted that sometimes an infected tooth has no other symptoms other than a blister and therefore recurring blisters should not be ignored as eventually the blister may close off and a large swelling will occur.
Recurring blisters can also be a type of herpes virus which lay dormant and recur intermittently. Antibiotics do not help such blisters, not even temporarily.
Consult your dentist if you experience recurring blisters to assess the cause of the blister and the best possible treatment.