Roseola infantum is a common acute exanthematous infectious disease in pediatrics, also known as baby roseola, caused by human herpesvirus types 6 and 7. To determine whether it is roseola, the main criteria are if the child is under two years old, especially infants aged 7 to 13 months, who exhibit a persistent high fever. During the fever, if the child’s fever subsides, they appear in good spirits and do not have other complications, then roseola should be highly suspected. In such cases, symptomatic treatment should be provided first, with a focus on hydration. If the temperature exceeds 38.5℃, give the child fever-reducing medication and continue to observe at home due to the persistent high fever, which lasts three to four days. Once the child’s temperature suddenly drops, carefully observe whether a rash appears on the trunk, neck, limbs, and facial area. If these symptoms are present, which match with the history of a high fever lasting three to four days followed by the appearance of a rash, the diagnosis is roseola infantum.