Roseola, a mild illness, gets its nickname from a list of six common childhood rashes. Young kids 6 months to 2 years are most likely to get it. It's rare after age 4. It starts with a cold, followed by a few days of high fever (which can trigger seizures). Then the fevers end suddenly. They're followed by a rash of small, pink, flat, or slightly raised bumps. It shows up first on the chest and back, then hands and feet.