Measuring a fever (by age)
Babies less than four to six months old
The most accurate way to take a baby’s temperature is rectally. To do this, make sure the thermometer is clean and apply a small amount of petroleum jelly around the bulb of the thermometer. Lay your baby on her back with her legs bent or on her tummy. Gently insert the thermometer about one inch into the rectum. An armpit reading is considered one of the least accurate ways to take a child’s temperature.
For the first four to six months of life, if your baby’s temperature is higher than 100.4 it’s a good idea to call your pediatrician. Remember, though, that illnesses don’t always cause a fever, so if your baby has other symptoms (difficulty breathing, a rash, or trouble feeding, for example), call your doctor even if her temperature is normal.
Babies at least six months old
You can take an ear temperature with an older baby or young child, although it will not be as accurate as a rectal temperature. For a baby over the age of six months, it’s a good idea to call your doctor if her temperature rises to 103F or if she has any fever lasting more than a couple of days.
For children over four or five, you can take an oral temperature.
As a general rule, if your young child has a fever of 103F for more than a couple of days, you should consult with your doctor, although your doctor will likely be just as interested in your child’s other symptoms (not simply the number on the thermometer) to determine a course of action. Pay attention to his appetite, fluid intake, presence and absence of cough, runny nose, loose bowels, headache, or rash to report these to your doctor as well.
Digital thermometers are recommended instead of glass mercury thermometers. As a matter of fact, mercury thermometers for in-home use are being phased out because of the potential risk involved with exposure to the mercury inside them.
Medication: Your doctor may recommend a fever-reducing medication such as infant or children’s acetaminophen or ibuprofen to bring down your child’s temperature – be sure to ask your doctor about the proper dosage and read your medication’s packaging and information carefully. Cough or cold medications should not be given to babies or young children.
However, many doctors are less likely to focus on the number on your child’s thermometer and more on her symptoms – encouraging you to treat her with medication if she is uncomfortable, not necessarily to bring down a fever. Remember that a fever is your child’s immune system doing its job, so some argue that small to moderate fever is a good thing.
You can also put your child in a lukewarm (not cold) bath, dress her lightly, and make sure she gets as much rest as possible. It’s also really important that you keep your baby or child well hydrated.
In some cases, a fever can cause a seizure in children. It’s estimated that one in 25 children will have at least one febrile seizure, and they usually occur in children six months to five years old.
Febrile seizures usually last a minute or two, during which a child convulses and can lose consciousness. Certain kids are more prone to having these seizures, and the tendency can run in families.
Scary as they may appear, a febrile seizure is usually not dangerous and there is no evidence that a short febrile seizure causes damage to your child’s brain or body. The vast majority of kids who have a seizure from a fever do not go on to develop epilepsy.
For more on what to do, treatments, and research on febrile seizures, look at the National Institutes of Health fact sheet.