Must-Know Health Numbers

That's the oral temperature that docs say qualifies as a fever

When your munchkin is burning up, it's difficult to remember that a fever is actually his body's way of posting a "No Vacancy" sign to viruses. "The body's temperature raises because most germs don't work as well at higher temps," says Gregg Alexander, D.O., a general pediatrician at Madison Pediatrics in London, Ohio. "Plus, the body's immune system functions better at a slightly elevated temperature." Once your child's temp exceeds 99.5°F (orally) or 100.3°F (rectally), it's considered a fever; keep him hydrated and give children's ibuprofen as directed. But an oral temperature of 103°F, a fever that lasts for more than 3 to 4 days, or any fever in an infant under six weeks old requires a call to the pediatrician.