Blisters on the mouth are commonly seen in herpes labialis, which requires antiviral treatment, but may also be pemphigus, allergic lipitis, which requires the use of hormones and other medications. 1. herpes labialis: blisters on the mouth may be the body herpes virus infection caused by herpes simplex or herpes zoster, herpes can appear on the lips such as the size of the tip of a needle dense small blisters, blisters are transparent, and soon can be broken vesicles, need to carry out antiviral treatment, generally use acyclovir or ribavirin drugs. 2. pemphigus: when their own autoimmune function problems may suffer from pemphigus, localized lips with blisters of varying sizes, hand pressure can push the blisters, easy to break secondary infection, preferred glucocorticosteroid drugs such as prednisone and other treatments, local application of antibiotic ointment. 3. Allergic lipitis: when the lips are in contact with allergic substances, may cause allergic lipitis, this time the first need to stay away from the substances that cause allergies, can be applied locally glucocorticoids and other drugs, oral anti-allergy drugs such as chlorpheniramine. Blisters on the mouth need to immediately go to the hospital to check the cause of the disease, under the guidance of the doctor to use medication.