Roseola is a very common viral illness characterized by fever followed by a rash.
The most common age to see this is between age 6 months and 3 years. Most children have had Roseola by the age of 2 years. Despite the high fever, most children do not seem very ill, often continuing to play normally, especially when the fever is low. There are usually no other symptoms except fever, but they may have a mild sore throat or slight congestion. The rash usually appears as the fever disappears, on the 3 rd to 5 th day.