Erythema behind the ear is one of the clinical manifestations of infectious erythema. It is a mild febrile infectious disease caused by a small viral infection, mostly seen in children under 12 years of age. It is prevalent in spring. So what are the causes of postauricular erythema? B19 virus is also considered to be the primary cause of chronic anemia. For a long time, it was thought to be a viral infection, but no laboratory evidence was available. It was not until 1983 that Andersorl et al. detected IgM and IgG antibodies to parvovirus B19 (PVB19) in the sera of 33 patients with erythema infectiosum, and thus concluded that this virus was the cause of erythema infectiosum. PVB19 can cause many clinical manifestations, ranging from no clinical symptoms to a typical rash. Some studies have found that PVB19 infection in pregnant women can cause miscarriage, stillbirth, and fetal edema.