So-called erythema multiforme is an acute, self-limiting, inflammatory skin disease, often accompanied by damage to the mucous membranes. The skin layer is polymorphic, and the rash of erythema multiforme is now found to be often widely published throughout the body, with edematous erythema, blisters, macules and hemorrhages. The damage of mucous membrane occurs more severely than the early stage, and the whole body mucous membrane can be involved, and blistering erosion, ulceration and bleeding can appear. Meanwhile, erythema multiforme is the most common damage to the eyes, manifesting as conjunctivitis, keratitis or ulceration, scleritis, etc., which may even lead to vision loss or blindness. Erythema multiforme is mostly seen in children and has a longer disease duration. At present, the cause of erythema multiforme is not clear, and many people believe that it is a kind of allergic reaction of the body to allergens, and most of them have a history of herpes simplex virus infection before the onset of this disease.