Remember: A fever is not an illness. It's usually just a sign that your child's immune system is fighting off a bacterial or viral infection, says Michael Devon, MD, a pediatrician in private practice near Philadelphia. Most of the bugs that cause a fever -- such as a cold, the flu, a stomach virus -- aren't dangerous and are treatable at home.
Check your child's other symptoms. How she acts and feels is usually a better indicator of how sick she is. (In fact, if your child has a high fever that doesn't mean she's sicker than if she has a low-grade one.) "If your child is lethargic, irritable, has a sore throat, ear or stomach pain, or pain when she urinates, call your doctor," says Dr. Devon. (Can't find any obvious source of infection? That also warrants a call.) And always get help immediately if you have a feverish baby under 3 months old, no matter what her symptoms are. Infants that young are more susceptible to certain types of infections, so your pediatrician needs to rule out serious illnesses right away.