Fever in babies and newborns

From time to time, your little one will have a raised temperature and may be sick. Obviously, this isn’t fun for your baby, and it may be stressful for you as a parent, especially if you’re not sure what might be causing the fever. Find out what symptoms to look out for, what temperature is considered a high fever in babies, and what you can do to bring down your little one’s temperature and keep them comfortable.

What Is a Fever?

A fever is not an illness in and of itself; rather it’s a symptom of an underlying illness, typically an infection. This temporary rise in temperature is a sign that the body is fighting illness, stimulating the white blood cells that battle infection.

Small rises in body temperature aren’t considered true fevers and are usually not a cause for concern. A true fever is when the body temperature shoots out of the normal range. Keep reading to learn more about normal temperature ranges and fevers for babies and young children.

Normal Body Temperatures and Fevers for Newborns, Babies, and Toddlers

Normal body temperature varies for everyone—babies, toddlers, older kids, and even adults. Not only that, but everyone’s temperature is highest between the late afternoon and early evening, and the lowest between midnight and early morning.

Infants, babies, and toddlers have a higher normal body temperature than older children, adolescents, and adults. Moreover, a child’s temperature will be different depending on their age, what activity they’re doing at the moment, and the time of day. In fact, a newborn’s normal temperature can vary up to 1 degree Fahrenheit throughout the day.

If you take your baby’s temperature from the rectum, ear, or forehead (using a temporal artery thermometer), a reading of 100.4 degrees Fahrenheit or higher generally indicates a fever. Rectal temperature readings are considered the most accurate for infants, especially those under 3 months old.

For an axillary reading—one that’s taken from your baby’s armpit—99 degrees Fahrenheit or higher is often considered a fever. The cutoff temperature tends to be lower because underarm measurements are less accurate.

What Causes Fever in Babies?

Fever is a symptom that can occur with any type of infection. This is why part of treating a fever will always involve treating the root cause of it, too.

Your child’s fever could be caused by any of the following:

Other Conditions Related to Fever in Babies

Teething, which starts for most babies at around 6 months old, may contribute to a small rise in your baby’s temperature, but teething isn’t usually the cause of a fever. (Learn more about the symptoms of teething.)

Immunizations. Infants and babies may get a spike in temperature after receiving routine vaccinations.

Heat-related illness or heatstroke is a rare but very serious condition in which surrounding heat, not infection or an internal condition, causes a sharp rise in body temperature. This problem can occur when a baby is in a hot environment such as a beach or an overheated car or when a baby is overdressed in hot, humid weather. Never leave a baby or child alone in a closed car, not even for a minute. If you think your child might have heatstroke, call 911 or take them to the emergency room.

Signs of a Fever in Babies

It may be difficult to tell if your baby has a fever. But if your baby looks or acts in a way that's out of the ordinary, and you think they may have a fever, it's a good idea to take their temperature. Keep in mind that a change in your baby’s behavior or activity level is often a better indicator of illness than how high the fever is.

The following signs, when paired with a fever, may indicate your baby is ill:

  • Change in behavior or activity level

  • Fussier than usual

  • Sleepier than usual

  • Warmer than usual

  • Appears flushed

  • Sweats more than usual

  • Thirstier than usual.

Be on the lookout for the following symptoms, which along with your baby’s fever are common signs of illness:

How to Take Your Baby’s Temperature

If you suspect your baby has a fever, especially after noticing some of the signs above, it’s best to use a digital electronic thermometer to take their temperature. Using a digital pacifier thermometer or a fever strip, kissing their forehead, or simply placing the back of your hand on their forehead are not accurate ways to gauge a fever.

Follow the instructions included with the thermometer, as each product can work a bit differently, or ask your healthcare provider to show you how to take your little one’s temperature. Make sure not to leave your child unattended when taking their temperature and keep separate thermometers for rectal and oral readings.

The best location for taking your baby’s temperature depends on their age. Here are some guidelines for which method to use when taking your baby’s temperature:

  • 0 to 3 months old. Take a rectal reading, which is considered the most accurate. Or, use a temporal artery thermometer, which is an infrared scanner that you pass over your baby’s forehead.

  • 3 to 6 months old. Take a reading rectally or under the arm. You can also use a temporal artery thermometer.

  • 6 months and older. This is the age where you can start taking your baby’s temperature using a digital ear (tympanic) thermometer. You can also continue taking a digital rectal reading with a digital thermometer or use a temporal artery thermometer. You’ll want to wait to take your child’s temperature orally until they’re 4 years old.

What to Do When Your Baby Has a Fever

When your baby has a fever, your first thought may be to bundle them up, especially if they also have the chills. However, this can make the fever worse. Don’t dress your child in extra clothes or cover them with a blanket—you want to encourage the heat to escape and the fever to go down, not up.

Here are ways to help lower your baby’s fever:

  • Cool the environment. Make sure your baby’s room is cool and comfortable. Consider setting up a fan to circulate cool air throughout the room.

  • Use lighter clothes. Dress your child in lightweight clothing. You want to encourage body heat to escape so that the temperature drops.

  • Give lots of fluids. Make sure your baby is getting plenty of fluids to prevent dehydration. Keep breastfeeding or formula-feeding your baby under 6 months old. For babies older than 6 months, you can additionally offer water or an oral rehydration solution.

  • Encourage rest. Take every opportunity to encourage your child to rest until the fever has passed.

  • Provide medicine. Your child’s healthcare provider may recommend a fever-reducing medication. We cover this in detail in the next section.

If the fever is a result of a contagious condition such as the flu or chicken pox, it’s best to keep your baby away from other children, older people, and anyone with a weaker immune system.

Fever-Reducing Medications

A fever may not require medication unless your baby is uncomfortable. Ask your child’s healthcare provider whether fever-reducing medicine is needed or not, and carefully follow any dosage instructions. Always consult with the healthcare provider before giving any medication of any kind to a baby who is younger than 2 months.

Aspirin is not recommended for children as it may lead to a serious condition called Reye’s syndrome. You may give acetaminophen or ibuprofen to your little one after you’ve gotten the green light from their provider. Acetaminophen may be recommended if your baby is 3 months or older, and ibuprofen if they are 6 months or older.

When it comes to dosage, follow the instructions on the product labeling. Dosage is typically based on your baby’s weight along with age. Always use the measuring device that comes with the product rather than a household teaspoon.

When to Call Your Baby’s Healthcare Provider

Your baby's healthcare provider may have more specific advice on when to be in touch, but in general, you need to call the provider when your baby is

  • 2 months old or younger and has a temperature of 100.4 degrees Fahrenheit or higher (call immediately)

  • 3 to 6 months old and has a temperature of 101 degrees Fahrenheit or higher

  • Older than 6 months and has a temperature of 103 degrees Fahrenheit or higher.

Make sure to let your child’s healthcare provider know the exact reading and the method (rectally, across the forehead, under the arm, or in the ear) you used to take your baby’s temperature.

Contact your child’s provider immediately or seek emergency care if your baby’s fever lasts for more than 24 hours, or if your newborn or older baby has any combination of these symptoms in addition to a fever:

  • Vomiting

  • Diarrhea

  • Uncontrollable crying

  • Fussiness

  • Sluggishness

  • Blue lips, tongue, or nails

  • A bulging or sunken spot anywhere on the head

  • A stiff neck

  • Limpness

  • Trouble breathing

  • Drooling

  • Seizure (see more on febrile convulsions below)

Febrile Convulsions

Rarely, a fever can trigger what is called a febrile convulsion—a seizure that can happen in children between 6 months and 5 years. This type of seizure usually lasts for a few seconds or up to one minute.

Witnessing your child having a febrile convulsion might be one of the scariest things you can imagine, but rest assured that this type of seizure is almost always harmless.

These are the signs of a febrile convulsion:

  • Your child looks unusual, stiffens, twitches, and rolls their eyes

  • Your child is unresponsive or passes out

  • Your child vomits or urinates during the seizure

  • Your child’s skin looks darker than usual.

If your baby is having a febrile convulsion, take the following steps:

  • Lay them on the bed or floor, away from any objects that could hurt them

  • Place them on their side to prevent choking

  • Loosen the clothing around their neck and head

  • Watch for any trouble breathing, such as their face turning blue; call 911 immediately for any breathing problems

  • If the seizure lasts more than 15 minutes, call 911 immediately.

Here are additional cautions when your little one is having a febrile convulsion:

  • Don’t put anything in your baby's mouth

  • Don’t hold or restrain your baby

  • Don’t administer fever-reducing medication

  • Don’t place your baby in a cool or lukewarm bath.

If your baby has had a febrile convulsion, let their healthcare provider know as soon as you can so you can schedule a checkup.

The Bottom Line

A fever is a symptom of an underlying illness, an infection such as an ear infection, the flu, or even the common cold. The best way to treat a fever is to also treat the underlying condition. In most cases, however, home treatment that includes hydration and rest are the best ways to bring down a fever.

If your baby under 2 months of age has a fever of 100.4 degrees Fahrenheit or higher, let their healthcare provider know immediately. Your baby’s healthcare provider will be able to diagnose the underlying cause of the fever and recommend treatment.

It’s natural to be uneasy when your baby has a fever, but with time and proper home care, your baby’s fever should subside. Always feel free to reach out to your child’s healthcare provider with any questions or concerns. Before long, your little one will be feeling better.