In general, the severity of a rash and fever does not relate to the severity of an illness. It is important to find out how ill the child feels or how the child is behaving.

Many viral illnesses can cause a rash and a fever of 103°F (39.4°C) or higher for short periods of time (up to 48 to 72 hours).

Newborns have immature immune systems. When they have fevers, they need to be evaluated sooner than older children with fevers. A fever that occurs with a rash in a newborn is impossible to assess over the telephone. A visit to a health professional is required.

High, persistent fevers are more likely to indicate a serious problem that requires a visit to a health professional. A persistent fever may be a symptom of a serious infection.

A rash that looks like a sunburn and that starts 2 days after a fever of 102°F (38.9°C) or higher may be caused by a rare condition called toxic shock syndrome.