Blisters under the lips may be shingles, herpes simplex, impetigo and so on. 1. Herpes zoster: When the body’s immunity is low, the varicella-zoster virus latent in the body will be activated, involving the nerves and skin, and will form clusters of blisters on the surface of the skin. 2. herpes simplex: herpes simplex is an infectious disease caused by the herpes simplex virus, mainly through kissing and other life close contact infection, the virus invades the skin and mucous membranes will proliferate locally, will form a latent infection locally, when the body’s immunity is low, the latent state of the virus will be activated to form a herpes, if it occurs in the mouth and lips area, it will be manifested as blisters under the lips. 3. Impetigo: Impetigo is caused by bacterial infections, including Staphylococcus aureus and Streptococcus b hemolyticus, etc. Bacteria will invade the epidermis to cause suppurative inflammation, which is mainly manifested as pimples, blisters and pustules. Blisters under the lips should go to the hospital for examination and symptomatic treatment for the cause.