Q: What is the best way to take a child's temperature? There are so many new kinds of thermometers and some are expensive.
A: First, let us say that most parents are more worried about temperature than they need to be. Fever can be an important sign of illness, but the exact degree of fever may not be important and fever is rarely, if ever, the only sign of serious illness requiring treatment. Since there is variation in normal body temperature throughout the day and between individuals, taking the temperature when the child otherwise appears well can make parents feel a child is ill when he or she is not.
When you need to look for fever, there is nothing wrong with using the standard glass thermometer. It does have three disadvantages. It takes a while, it breaks (and cannot be used in the mouth of a young child who might bite it in two) and some parents find it difficult to read. However, it is inexpensive and very accurate. All other methods of temperature taking are compared with a rectal temperature taken with a glass thermometer. It is considered the standard.
New technology has produced thermometers which are easier to use. They don't take as long and are easier to read because a number lights up like a digital watch. Some are designed to take the temperature from the skin or the ear. Many children and parents prefer those sites to the mouth or rectum. Thermometers used on the skin usually give a lower reading than those used in the mouth, and a temperature taken from the mouth is lower than one taken in the rectum. When reporting the temperature to your doctor, it may be important to say how you took it.
The bottom line is that you may take your child's temperature using any of these thermometers, but need only do so when your child seems ill or your doctor directs you to do so. In choosing among thermometers, you may decide to value lower cost over speed and convenience.
Dr. Wilson is director of general pediatrics at the Johns Hopkins Children's Center; Dr. Joffe is director of adolescent medicine.