There are many causes of clear blisters on the inside of the mouth, such as herpes, mucous gland cysts, autoimmune diseases, trauma and so on. 1. Herpes: oral infection with herpes virus can induce herpes attacks, thus leading to the phenomenon of clear blisters on the inner wall of the mouth, which can show clusters of dense blisters, and ulcerated surfaces can be formed after rupture. 2. Mucous gland cysts: salivary gland glands suffered trauma, or congenital dysplasia and other factors, can lead to the opening blockage, thus forming mucous gland cysts, so there will be the phenomenon of clear blisters on the inner wall of the mouth. 3. autoimmune diseases: autoimmune pemphigus, pemphigus-like diseases, can also lead to the phenomenon of clear blisters on the inside of the mouth, the phenomenon is relatively rare. 4. Trauma: clear blisters on the inside of the mouth may also be due to trauma, such as burns, bites, etc., the phenomenon of clear blisters can occur. Clear blisters on the inside of the mouth have many reasons, after the symptoms need to go to the hospital in time to improve the examination, diagnosis and follow the doctor’s instructions to take standardized treatment, so as not to lead to adverse consequences.