Blisters around the lips when fatigued are mostly due to herpes simplex induced by exertion. Herpes simplex is a common skin disease caused by herpes simplex virus infection, characterized by clusters of blisters, which can heal on their own, but when cold, fatigue, stress and other situations, the virus in a latent state can be activated, which can trigger herpes recurrence. It is mainly manifested at the junction of skin and mucous membranes, such as the corners of the mouth and the edges of the lips. Usually the number of blisters is not large, pin-shaped or rice grain size, at the beginning of the skin mucous membrane will have pain or burning sensation, followed by the formation of blisters, the appearance of typical clusters or scattered distribution of multiple blisters, blisters rupture will appear vesiculation, oozing, later skin drying, crusting, the symptom is mostly relieved within 1 week. This disease is mostly self-limiting, avoid excessive stress, pay attention to personal hygiene and cleanliness, if the symptoms are serious, it is recommended to consult a doctor in time.