Here's a guide to help you determine how sick your child is and how to help him get well.
Step 1: Take a Temperature
A rectal reading is the "gold standard," Dr. Krol says. Doctors really prefer that you use this method, especially with children less than 3 months old. With a digital thermometer and a lubricant, such as petroleum jelly or aloe vera, you can get a reading in a matter of seconds. (Don't use glass thermometers, which can release dangerous mercury into the air if they break.) But doctors know that many parents are averse to "going there," and many babies will fiercely protest. So what are the alternatives?
For children under age 4, digital thermometers work only when used under the arm or in the rectum, because children that young lack the patience and coordination to keep a thermometer tightly in their mouth. If you take an underarm temperature, it's a screening tool at best. "If you get higher than 99 degrees, you should recheck with a rectal," says Dr. Krol. Ear thermometers work great when used correctly, says Barbara Huggins, MD, professor of pediatrics at the University of Texas Health Center, at Tyler. "You need to insert it into the ear canal," she says. "If it's too small, there's a big clump of wax; if you don't have it lined up with the eardrum, you will get a falsely lower result." Dr. Krol recommends using an ear thermometer starting at age 6 months (before that, you guessed it, he'd prefer a rectal). If you're getting a different reading from two ears (this is common, according to Dr. Krol), pick one ear and stick with it. Use that reading to evaluate if the temperature is going up or down.
Step 2: Make a Plan
What constitutes a fever? Your child's age is key in interpreting his temperature. According to the American Academy of Pediatrics (AAP), if your child is less than 2 months old and is running a fever of 100.4 degrees or higher, don't just call the doctor. Your baby should be seen immediately, in the office or, if it's after hours, in an emergency room. (Many doctors even feel that a 3-month-old with a 100.4-degree or higher temperature should get immediate medical attention.) The AAP recommends that you call your pediatrician if your infant is between 3 and 6 months and has a fever of 101 degrees, or if your baby is more than 6 months and has a fever higher than 103 degrees. After age 1, if your feverish kid is eating well, playing, and is in a good mood, don't run to the phone. The illness can be treated at home.
Keep in mind that fevers aren't always the result of an illness. Heat stroke is possible if your baby has been in a hot place, such as at the beach or in an overheated car, or if he's overdressed. If his temperature is more than 105 degrees, move him to a cool place as quickly as possible. Remove his clothing, give him a sponge bath, and then get him to the doctor as soon as possible. A temperature below 105 degrees isn't an emergency, although you should call your doctor if you're concerned.
A recent vaccination also can bring on a fever, especially in 2-month-olds. That's when, often at a single doctor's visit, they get shots for diphtheria, tetanus, pertussis, polio, hepatitis B, pneumonia, and meningitis. One out of 100 infants who received this all-in-one round of vaccines was treated in an emergency room for a fever of 100.4 degrees or higher, according to one recent study that looked at the health records of 4,000 infants. "The vaccination at 2 months of age is a tricky one," Dr. Krol says. "If the baby was fine, got his 2-month shot, and went home and got a fever immediately, the doctor might say, 'Is the child acting okay?' If Mom says yes, he's just got a fever, a lot of pediatricians might say, 'Let's first give him 24 hours and then give him acetaminophen, if needed.' But it should be a decision made by the parent and doctor."
Teething might also be linked with fever, although parents seem to hold more faith in this connection than doctors do. Teething may occasionally cause a low-grade fever below 101 degrees, says the AAP, but if the fever goes higher, says Dr. Krol, illness is the more likely cause.