Common causes of small blisters (medically known as blisters) on the lips include herpes simplex, impetigo, contact dermatitis, and so on. 1. Herpes simplex: Herpes simplex is caused by herpes simplex virus infection, which occurs on the lips and genital area, manifesting as clustered, painful blisters on the skin and mucous membranes, followed by pustules and other symptoms. 2. Impetigo: Impetigo is a suppurative inflammation caused by bacterial infection, infectious, can occur on the lips, manifested as erythema, blisters, pustules, easy to break and honey yellow pus crust and other symptoms. 3. Contact dermatitis: this disease is due to skin contact with exogenous pathogenic substances, such as animal fur, dust, chemical fibers, detergents, etc., stimulate the skin or trigger an allergic reaction. It can occur on the side of the lips, manifested as red spots, swelling, pimples, blisters, and even large blisters and other symptoms. It is recommended that patients according to their own situation, if necessary, to the regular hospital dermatology department, after a clear diagnosis, follow the doctor’s instructions reasonable treatment.