Choosing a Fever Thermometer

by Christine Haran

Dads and moms who find themselves in the drugstore trying to buy a thermometer in a hurry may be overwhelmed by their choices. The thermometer market has broadened in the last decade: While parents once had had two choices, there are now five or six.

Before selecting a thermometer, parents should know that what they are measuring is the closest possible approximation to body core temperature, which is the temperature inside the body. Also, body temperature varies at different times of the day and in different parts of the body. For example, normal temperature is 98.6° F (37° C) when taken orally and about 99.6° F (37.6° C) rectally. According to the American Academy of Pediatrics, given natural fluctuations, most pediatricians consider a reading over 100.4° F (38° C) a sign of fever. Fevers around 101° F (38.4° C) fever are considered low grade, while high fevers are over 103° F (39.4° C).

One easy way to narrow the thermometer field is to avoid glass mercury thermometers. Digital thermometers are a safer choice because mercury, which is harmful to humans and the environment, can be released if a glass thermometer breaks. And according to the American Medical Association, digital thermometers are just as accurate as glass mercury thermometers. (Mercury should be disposed of as a hazardous waste; Call your local health department or visit www.earth911.org for an approved mercury disposal location.)

Among digital thermometers, a popular though expensive option is the ear thermometer, which measures the temperature in the ear canal. This instrument is considered quick, comfortable and relatively accurate, but Lorraine Stern, MD, a clinical professor of pediatrics at the University of California Los Angeles, cautions that it doesn't work well in small infants because their soft ear canals may temporarily collapse when the thermometer is inserted and provide a reading that is too low.

For infants under six months, Dr. Stern recommends using a rectal thermometer. This is also a good option for children under four or five, who are too young to use an oral thermometer. Some parents may prefer the axillary thermometer, which measures the temperature under the armpit, though a recent study found that the normal axillary temperature runs low and should be interpreted with caution.

Dr. Stern warns against using forehead thermometers, which are sold in strips, and pacifier-thermometers, neither of which give accurate readings.

She also reminds parents that, except for infants, more than just the number on the thermometer should be considered when determining if you need to take your child to the doctor. "A child with a 101° F (38.4° C) fever who is moaning and pale and looks out of it is sicker than a child with an 103° F (39.4° C) fever who is running around," Dr. Stern explains, adding that while a fever in child is often scary for the parent and uncomfortable for the child, it is part of the way the body fights infection.

In 2 percent to 5 percent of children between six months and five years fevers can trigger seizures known as febrile seizures. Febrile seizures are not harmful but need to be discussed with the child's pediatrician.

Besides weighing factors such as your child's appearance and energy level, parents should also consider their child's age and the length of time they've had the fever. "In infants under two months with a fever, bring them in right away," Dr. Stern says. "In a four-year-old, you can wait a day or two and see what happens if they don't look bad."

"Any temperature that you take is an approximation of body temperature," Dr. Stern continues. "It the child's temperature seems too high or too low, check it with another method. And you may have to combine such things as the thermometer reading, how your child looks and even mother's lips on the forehead."

Christine Haran has been a health journalist for more than seven years, and her work has appeared in Woman's Day, MAMM Magazine, Bride's Magazine, Publishers Weekly and other publications. In 2003, she received an Excellence in Women's Health Research Journalism Award from the Society for Women's Health Research. Haran has a master's degree in journalism from New York University and a bachelor's degree in english from Skidmore College.