All kids get a fever from time to time, and most fevers usually don't indicate anything serious. Fever itself causes no harm and can actually be a good thing – it's often the body's way of fighting infections.
But when your child wakes in the middle of the night flushed, hot and sweaty, it's easy to be unsure of what to do next. Should you get out the thermometer? Call the doctor?
Here's more about fevers, including when to contact your doctor.
What is a fever?
Fever happens when the body's internal "thermostat" raises the body temperature above its normal level. This thermostat is found in a part of the brain called the hypothalamus. The hypothalamus knows what temperature your body should be (usually around 98.6 °F/37 °C) and will send messages to your body to keep it that way.
Most people's body temperatures change a little bit during the course of the day – temperatures are usually a little lower in the morning and slightly higher in the evening and can vary as kids run around, play and exercise.
Sometimes, though, the hypothalamus will "reset" the body to a higher temperature in response to an infection, illness or some other cause. Why? Researchers believe that turning up the heat is a way for the body to fight the germs that cause infections, making it a less comfortable place for them.
Although it can be frightening, a fever can be a good thing because it's often the body's way or fighting infections.
Pay attention if your child experiences the following:
- a temperature of 100.4° F or higher in infants younger than 3 months
- a temperature of 102.2° F or higher in children 3 months to 3 years
- an older child who has a fever and:
- Appears sick
- Develops a rash
- Has persistent diarrhea
- Shows signs of dehydration
- A chronic medical problem
What causes fevers?
It's important to remember that fever by itself is not an illness – it's usually a symptom of another problem. Fevers can be caused by a few things, including:
Infection: Most fevers are caused by infection or other illness. A fever helps the body fight infections by stimulating natural defense mechanisms.
Overdressing: Infants, especially newborns, may get fevers if they're over-bundled or in a hot environment because they don't regulate their body temperature as well as older children. However, because fevers in newborns can indicate a serious infection, even infants who are overdressed must be checked by a doctor if they have a fever.
Immunizations: Babies and kids sometimes get a low-grade fever after getting vaccinated.
When is a fever a sign of something serious?
In healthy kids, not all fevers need to be treated. High fever, though, can make a child uncomfortable and make problems – such as dehydration – worse. Doctors decide on whether to treat a fever by considering both the temperature and a child's overall condition.
Kids whose temperatures are lower than 102 °F (38.9 °C) often don't need medicine unless they're uncomfortable. There's one important exception: If an infant 2 months or younger has a rectal temperature of 100.4 °F (38 °C) or higher, call your doctor or go to the emergency department immediately. Even a slight fever can be a sign of a potentially serious infection in very young babies.
If your child is between 2 months and 3 years old and has a fever of 102.2 °F (39 °C) or higher, call to see if your doctor needs to see your child. For older kids, take behavior and activity level into account. Watching how your child behaves will give you a pretty good idea of whether a minor illness is the cause or if your child should be seen by a doctor.
The illness is probably not serious if your child:
- is still interested in playing
- is eating and drinking well
- is alert and smiling at you
- has a normal skin color
- looks well when his or her temperature comes down
What else should I know?
All kids get fevers, and in most cases they're completely back to normal within a few days. For older babies and kids, the way they act can be more important than the reading on your thermometer. Everyone gets a little cranky when they have a fever – this is normal and should be expected.
But if you're ever in doubt about what to do or what a fever might mean, or if your child is acting ill in a way that concerns you even if there's no fever, always call your doctor for advice.
Learn more about our dedicated Pediatric ER on our pediatric ER page and find a pediatric specialist on our pediatric care page.