Roseola (also known as sixth disease, exanthem subitum, and roseola infantum) is a mild, self-limited illness that mainly affects children and is defined by its classic exanthem. Human herpesvirus (HHV)-6 and HHV-7 have been implicated as causal agents. Antibodies, which are almost universally found in pregnant individuals, are protective prior to the age of 6 months. Infants with roseola are typically between the age of 6 months and 1 year, with 90% of cases occurring in children aged younger than 2 years. The disease course classically begins with a high fever typically greater than 38.9°C (102°F). The infant or child is otherwise well appearing, and the fever usually subsides on the fourth day.

The fever is followed immediately by the onset of asymptomatic, rose-pink, blanchable macules and papules 2-3 mm in diameter that begin on the trunk and may spread to the neck, upper extremities, and lower extremities. The rash typically lasts 1-2 days but can resolve more quickly.

Roseola is the cause of up to one-third of all febrile seizures and accounts for greater than 10% of undifferentiated febrile illnesses in children younger than 2 years.

While this disease is self-limited, it accounts for a large portion of emergency department and clinic visits for fever in infants and young children and often leads to unnecessary antibiotic prescriptions.