Fever is nothing to worry about in itself. It just indicates that there is something wrong with the body. It may cause the baby to look flushed or make his body hot. You may give and infant pain reliever recommended by your pediatrician to a child more than one year old to lower his fever, only if he is happy and do not have other symptoms such as cough or runny nose. A lukewarm sponge bath may also help to reduce the fever.
However, a persistent fever surely becomes a source of concern. Call your doctor immediately if the rectal temperature of a baby less than 3 months old is over 100.4°F; over 101°F for a baby who is 3 to 6 months old and 103 °F for babies older than 6 months. Let the condition of your baby guide you rather than how high the fever is. Even if the fever is low but the baby looks pale, is lethargic or suffers from pain, you need to visit your doctor immediately.