Herpes simplex refers to an acute viral dermal disease caused by herpes simplex virus (HSV), which attacks mostly the juncture of the mucous membrane and the skin, and occurs often with fever or during high fever, characterized clinically by mixed groups of blisters, recovery one week after the onset and easy recurrence.This disease is associated with human herpes simplex virus. In accordance with difference in the nature of antigen, herpes simplex virus can be divided into Type I and II (HSV-I , HSV-II ).

HSV-l is mostly related to nongenital infection. HSV-II often occurs after adolescence and is mostly infected by sex contact, with the harms mostly in the genital region. It is believed in Chinese medicine that this disease belongs to the category of "Heat Boil", mostly caused by internal accumulation of heat in the lung and stomach or in the spleen and stomach and invasion of external seasonal toxins steaming on the head and face, or by downward transmission of dampness and heat into the lower energizer.