When your baby has a
fever, especially if it's their first one, it can be alarming. Keep in mind that fever, which is
sign or symptom of illness, is usually a good sign that the body is fighting off an infection. Fever stimulates immune defenses, such as white blood cells, that attack and destroy invading bacteria and viruses. But it's important to figure out the cause of your baby's fever so it can be treated, and to help keep your child
hydrated and comfortable.
What's considered a fever?
A child's normal temperature can vary, depending on age and activity level. Time of day can also affect the reading. Body temperature is highest in the late afternoon and early evening, for example, and lowest at midnight and early morning. Plus, infants tend to have higher temperatures than older children.
Rectal temperature for infants
Ordinarily, a rectal temperature reading of 100.4 degrees Fahrenheit (38 degrees Celsius) or higher is considered a fever. A rectal reading is the most reliable and accurate for infants, especially babies under 3 months old.
If you take an oral (mouth), tympanic (ear) or temporal artery (side of forehead) temperature reading, you should still generally use 100.4 degrees Fahrenheit or more as the cutoff for a true fever. However, axillary (underarm) temperature measurements may have a lower cutoff to be considered a fever.
How do I know if my baby has a fever?
Whenever you think your child has a fever, take their temperature with a
thermometer. Feeling their forehead or skin on other parts of the body is not accurate, especially if your baby is having chills. Using temperature sensitive tape or "fever strips" also is not reliable.
Avoid using an ear thermometer for babies under 6 months old, since their ear canals are too small to allow an accurate reading.
Causes of fever in babies
Fever in babies can develop with illnesses such as:
The most serious conditions that can cause fever are infections blood (sepsis) and the brain and spinal cord (meningitis).
Fever in newborns
If your baby is 3 months of age or younger and has a rectal temperature of 100.4 degrees Fahrenheit (38 degrees Celsius) or higher, call your pediatrician immediately. This is very important, even if your baby shows no other signs or symptoms of being ill.
The doctor will need to examine the baby to rule out any serious infection or disease. You also may need to notify the doctor if your child is between 3 and 6 months and has a fever of 101 degrees Fahrenheit (38.3 degrees Celsius) or greater, or is older than 6 months and has a temperature of 103 degrees Fahrenheit (39.4 degrees Celsius) or higher. Such a high temperature may point to a significant infection or dehydration, which may need treatment.
Febrile seizures
In children between 6 months old and 5 years of age, fever can trigger seizures. These are called
febrile seizures or febrile convusions. Febrile seizures tend to run in families and usually happen during the first few hours of febrile illness.
During a febrile seizure, a child may get an odd look on their face for a few moments, then stiffen or twitch and roll their eyes. They will be unresponsive for a short time. Their skin may also appear a little darker than usual during the episode.
The entire febrile seizure typically last less than one minute—or even just a few seconds—though it can seem like forever to a frightened parent. It is reassuring to know that febrile seizures are almost always are harmless, causing no lasting damage to the brain or nervous system. However, if your baby has a febrile seizure, be sure to tell your pediatrician promptly. If your child is having trouble breathing or the febrile seizure does not stop within 15 minutes, call 911.
Raised body temperature from heatstroke
Fever should not be confused with
heat-related illness, or
heatstroke. This is not caused by infection. Instead, this dangerous condition is caused by surrounding
heat in their environment and dehydration. With heatstroke, body temperature can rise to dangerous levels (above 105 degrees Fahrenheit [40.5 degrees Celsius]). Dozens of children die each year when left unattended in closed,
overheated cars, for example. Never leave your baby alone in closed car, even for a few minutes. Babies can also develop heatstroke if
overdressed in hot, humid weather.
If you think your child has heatstroke,
call 911 or go to the emergency department right away.
Does teething cause fever?
Teething, which often starts at about 6 months of age, can cause a slight rise in your baby's body temperature within the normal range. However, research shows teething does not cause a true fever. If your child seems particularly miserable or has a fever higher than 100.3 degrees Fahrenheit (38 degrees Celsius), it’s probably not from teething; you should consult your pediatrician, as your baby may be sick.
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