A lot of small blisters (medically known as blisters) on the mouth can be considered to be related to the occurrence of herpes simplex or impetigo. 1. Herpes simplex: it can be caused by the herpes simplex virus that spreads through skin wounds, oral mucosa, etc. At the onset of the disease, erythema may appear on the lips, followed by blisters, several or a dozen distributed in clusters. 2. impetigo: often caused by staphylococcus aureus, type b hemolytic streptococcus and other pathogens, pus bacteria often invade the delicate skin of infants and young children, the first time can cause a number of tiny red spots or blisters, and then can be extended to pustules, and vesicles and scabs. The mouth has a lot of small blisters, and may be caused by other diseases, it is recommended to go to the hospital dermatology department in a timely manner, in accordance with the doctor’s instructions on the cause of the symptomatic treatment.