Erythema is a microvascular malformation, a congenital, low blood flow, intra-dermal capillary dilation malformation. Commonly known as the red birthmark, it is easy to cause great psychological stress to patients because its location is usually in a prominent place on the face, and its effects should not be underestimated. Erythema nevosum is a benign congenital vascular lesion, the incidence of which is 0.3-0.5%. Its pathological change is the congenital weakness of capillary wall causing the dermal superficial capillary dilation. The lesion is mainly concentrated in the middle and upper dermis, and with age, the lesioned skin appears to thicken and gradually extend to the subcutaneous tissue, consisting of many abnormally dilated mature capillaries.