There are many causes of clear raised blisters in the mouth, such as trauma, herpes-like viral infections, pemphigus and so on. 1. trauma: accidental bites, or eating too hot food, etc., may cause trauma to the oral mucosa, thus causing the phenomenon of oral long transparent raised blisters. 2. Herpes virus infection: when the body’s immunity is reduced, if the herpes virus invades the body, herpes can be induced, thus showing the phenomenon of long transparent raised blisters in the mouth, which may also be accompanied by fever, pain and other phenomena. 3. Pemphigus: Pemphigus is an autoimmune disease, which may be related to ultraviolet irradiation, viral infection, drug stimulation and other factors, and may manifest the phenomenon of long, clear, raised blisters in the oral cavity, accompanied by increased salivation, lymph node enlargement and other phenomena. There are many reasons why the mouth long transparent raised blisters, after the emergence of symptoms, it is recommended to go to the hospital in a timely manner to improve the examination, under the guidance of the doctor to take standardized treatment, do not take care of, so as not to lead to adverse consequences.