Clear blisters on the inside of the lower lip may be caused by infection, external irritation or mucous cysts. 1. Infection: Bacterial or viral (e.g. staphylococcus, herpes simplex virus) infections can lead to edema and oozing of lip mucosal tissues, resulting in blisters or herpes and other symptoms; it is necessary to consult a doctor for anti-inflammatory or antiviral treatments such as antibacterial (e.g. cephalosporin) or antiviral medications (e.g. amoxicillin, aciclovir, etc.) to control the symptoms. 2. External stimuli: burns or bites can also lead to blisters caused by the exudation of tissue fluid from the lip mucosa; the wound should be kept clean to promote healing and erythromycin ointment should be applied locally as prescribed by the doctor to prevent infection. 3. Mucous cysts: this condition is a common benign cyst on the lips, which is caused by damage to the salivary glands and leads to blisters where saliva cannot be normally secreted into the oral cavity; it is necessary to seek medical treatment for mucous cysts removal surgery to cure the above symptoms. Blisters on the lower lip, it is recommended to consult a doctor for symptomatic treatment to avoid delaying the condition, the use of drugs need to follow the doctor’s instructions.