Roseola is a generally mild infection that usually affects children by age 2. Roseola often starts with a sudden high fever (103°F to 105°F) that lasts 2 to 3 days, although it can last up to 8 days. The rapid increase in temperature may be the first sign of Roseola. Within 12-24 hours of the fever breaking, a rosy-pink rash may appear mostly on the torso, neck, and arms. The rash is not itchy and may last 1 to 2 days.