If it's roseola infantum, it is a febrile rash disease. Generally, fever might last about two to three days. After that, a rash will appear, usually after the fever settles down. Initially, this rash typically starts on the face and head, and then spreads to the trunk, chest, back, and can even cover the entire body. These rashes are small papules and generally fade away within two to three days without leaving any scars. Once the rash appears, there's no need to worry, as the body temperature should start to decrease.