Pediatrics / Children's Health

What to know about fever in babies

Fever in babies is a common concern among caregivers, though a fever itself is not dangerous.

A fever means that a baby’s body is fighting off an infection. When is fever a cause for concern and how can you comfort a baby with fever?

Caregivers may worry when they notice that a baby has a fever, although fever is a sign of a healthy immune system. Newborns, however, have more vulnerable bodies and a fever can signal a serious infection.

In this article, we look at the causes of a fever in babies, what it means, and when to see a doctor. We also discuss how to care for a baby with a fever.

Identifying fever in babies

Mother holding baby with a fever on their lap, with thermometer and holding baby's head for temperature
A baby with a fever may not be ill, as babies are less able to regulate their body temperature.

When taking a baby’s temperature, people can use a rectal thermometer for the most accurate results.

Fever in a child depends on the method of taking the temperature:

  • above 100.4°F using a rectal thermometer
  • above 100°F using an oral thermometer (not accurate in infants)
  • above 99°F using an armpit thermometer

By itself, fever does not necessarily signal a serious illness. If the baby’s behavior is normal, they are likely to be OK. However, if a baby under 3 months of age has a fever higher than 100.4°F when taken rectally, a caregiver should call a doctor.

The severity of a fever does not always correlate with how sick the child is.

Babies’ body temperatures can rise for many reasons other than illness, including extended crying, sitting in the hot sun, or spending time playing. Their temperature may also rise a little when they are teething. None of these things causes a fever.

The normal temperature for babies depends on their age:

  • for infants aged 0–2 years, normal ranges are 97.9–100.4°F when taken rectally
  • for newborns, the average body temperature is 99.5°F

The normal body temperature ranges differ for adults, children, and babies.

A baby’s body is less able to regulate temperature than an adult’s, meaning it can be more difficult for them to cool down during a fever. Their bodies are naturally warmer than an adult’s body because they are more metabolically active, which generates heat.

Common causes of fever in babies

A fever is a symptom of an illness, not an illness itself. Children have fevers when their immune system is fighting off an infection.

Common causes of fevers in babies include:

Babies can also develop fevers following a skin injury. This usually means there is an infection.

Rarely, heat-related illnesses can cause high temperatures in babies. Babies are less effective at controlling their body temperature than adults, so they are more vulnerable to very hot weather.

Dressing babies in weather-appropriate clothing, keeping them out of hot sun, and keeping them indoors when the weather is very hot will help regulate their body temperature.

Are fevers dangerous for babies?

pharmacist looking at prescription medication in pharmacy
A doctor may recommend antibiotics to treat the cause of a baby’s fever.

Some parents worry that fevers are dangerous, but they almost never are.

Fevers of up to 105°F are common in young babies and children whose temperatures often get much higher than an adult’s temperature.

A fever is simply a sign that a baby is fighting an infection. The underlying infection may be harmful, and many infections require antibiotics or other treatment, but the fever itself is just a symptom.

Treating the fever will not make the infection go away. Instead, caregivers should look at fevers as a sign that the baby’s immune system is fighting infection. For this reason, they should carefully monitor their child for signs of complications.

Infections can be more dangerous in newborns, and so it is important to see a doctor for a fever or other signs of infection in very young babies, such as difficulty breathing or severe congestion.

Some parents may have heard stories about fevers causing brain damage. This can only happen if the temperature rises above 107°F, which is very rare. When temperatures are below this number, there is no need to take drastic measures, such as ice baths, to lower the child’s fever.

For 2 to 5 percent of children between 6 months and 5 years, a fever can cause a seizure. These seizures can be worrying, but they are not typically harmful. Doctors call them febrile seizures.

Febrile seizures do not cause brain damage or increase a child’s risk of epilepsy. Even long seizures, or those that last longer than 15 minutes, usually have a good outcome. Prolonged seizures may, however, mean a child is more likely to develop epilepsy.

The biggest risk of febrile seizures is that a child may fall, hit their head, or suffer a similar injury. Caregivers should monitor children during a seizure to prevent injury and report any seizures to a doctor.

How to care for a baby with a fever

The American Academy of Pediatrics recommend that caregivers monitor children for signs of illness and make their babies comfortable instead of treating the fever itself.

To care for a baby with a fever:

  • Monitor the baby’s activity level and overall comfort. Babies who seem happy, alert, and comfortable may not need treatment.
  • Ensure the baby remains well hydrated. Fever increases the risk of dehydration. Nurse or give formula on demand. Older babies should drink plenty of water. In some cases, a healthcare professional may recommend using an electrolyte drink to prevent dehydration.
  • Monitor the baby for signs of dehydration that can include not urinating as often as usual, sunken eyes, chapped lips, or very dry or pasty looking skin.
  • Avoid waking a sleeping baby to give them anti-fever medication.
  • Under a doctor’s supervision, people can give a baby anti-fever medication if it is in pain or uncomfortable from the fever. The baby’s weight determines the dose, so follow the label instructions carefully. Call a doctor before giving new medication to a baby, especially a sick one.
  • Do not send a sick baby to daycare or take them to places where babies or other vulnerable people may be, as this can spread infection.

When to see a doctor

Call a doctor or seek medical care if a baby has a fever and one of the following:

  • The baby is inconsolable, lethargic, or seems very sick
  • A fever lasts longer than 24 hours in a baby younger than 2 years old without any other symptoms.
  • The fever rises above 104°F.
  • The fever does not go down with medication, or the child still seems sick with medication.
  • The baby is taking antibiotics but does not seem better within a day or two.
  • The baby has signs of dehydration, including dry lips or a sunken soft spot on top of their head.
  • The baby has a weak immune system for a separate reason.
  • The baby is younger than 3 months old.

Go to the emergency room for a fever if:

  • The baby is a newborn.
  • A baby has a seizure for the first time.
  • A baby has a seizure that lasts longer than 15 minutes.
  • The baby’s temperature rises to 107°F or higher.

Fever in newborns

Father holding newborn baby in lap
If a newborn has a fever, they require immediate medical attention.

A fever in a newborn may be a sign of a serious medical condition. Newborns are more vulnerable to infections, and so it is important to take seriously any signs that a newborn has an infection. Call the doctor if a newborn has a fever or other signs of illness.

One of the biggest concerns with newborns is respiratory illness. Newborns breathe more through their noses than older infants and children, so congestion can make breathing more difficult. They also have smaller airways.

Lack of oxygen can seriously injure a newborn. If a baby has trouble breathing, call a doctor even if their fever goes down.

Signs that a newborn is having trouble breathing include:

  • wheezing or grunting
  • flaring the nostrils when breathing
  • white or blue skin, especially around the nail beds, or on the mouth or tongue
  • pulling in the muscles around the ribs when breathing

If a baby has breathing problems and a fever, it should be taken to the emergency room immediately.

Conclusion

Young children and babies sometimes get high fevers, but otherwise behave normally.

Carers can use a child’s behavior as a cue. If a baby seems fine but has a fever, the illness is probably a minor one that will soon pass.

Lethargy, excessive crying, and other signs of serious illness are important to address even if a child’s fever is fairly low. Fever means that the immune system is working hard to fight an infection.

Caregivers do not need to treat the fever itself, but they can comfort the baby and treat the symptoms instead. Caregivers who are unsure whether a baby’s symptoms are serious should call their healthcare provider.

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