My pager goes off at 3 a.m. As I fumble for the phone and dial the number, I grumble to myself, "This better be important!" But when I hear the worried voice of the mom on the line, telling me her child is burning up with a fever, my grumpiness fades. I ask several specific questions and determine that the baby isn't urgently sick. My advice: Give the child a dose of acetaminophen and call our office first thing in the morning.
Thankfully this scenario doesn't occur every night, or I would never get any sleep. But many of the late-night calls I receive are about fever, and it's hardly surprising that parents are concerned when their child turns into a rag doll in their arms. But fever itself is rarely dangerous: It's a sign that the body is fighting an infection.
What Causes Fevers?
Fever is the body's normal response to an invading germ. When the immune system detects a virus or bacteria, an increase in white blood cells sends a message to the brain to raise the body's temperature, helping it fight the infection.
Fever itself isn't an illness. Like the "check engine" light on your dashboard, a fever is a warning that something needs attention. Fevers that are caused by viruses rather than bacteria don't respond to antibiotic treatment. Some common viral causes of fever are roseola (identified by a rash on the upper body that emerges after the fever breaks), Coxsackie virus (also known as hand-foot-and-mouth disease, it causes painful sores or blisters in these areas), as well as the common cold. Bacterial causes of fever, which will respond to antibiotics, are certain ear infections (though your doctor may take a wait-and-see approach before writing a prescription at the first sign of infection), some forms of pneumonia, and sinus and bladder infections.
The Degree of the Problem
What constitutes a fever? I generally consider any temperature under 100.4 degrees to be normal. Between 100.5 and 103 is a moderate fever, and anything over 103 is a high fever. Infants generally have a higher temperature than older children, and everyone has a slightly higher reading between the late afternoon and early evening.
The rectal method is considered the most accurate, and is recommended for infants younger than 3 months of age. For these babies, it's important to know the exact temperature to determine the proper course of action. After 3 months, an underarm or pacifier thermometer is fine. They're less invasive than rectal, and it isn't as important to know the exact temperature in a baby that age. Since thermometers can vary, I prefer for parents to tell me both the temperature and the method used for measurement so I can decide how to interpret the information.