It’s natural for panic to set in the minute baby feels warm to the touch. Especially if it’s baby’s first fever. Odds are it’s going to happen sooner or later, so your best defense is to be prepared to spot the telltale signs of baby fever.
What Is a Fever for Baby?
First, knowing what is a fever for a baby is key: 100.4° Fahrenheit (38° Celsius) or higher is not a normal body temperature for babies and therefore constitutes a baby fever, says pediatrician Tanya Altmann, MD.
How to Tell If Baby Has a Fever
One key baby fever warning sign is heat. “When your baby has a temperature, he or she feels like a little radiator,” says Rallie McAllister, MD, MPH, family physician and coauthor of The Mommy MD Guide to Your Baby’s First Year. And since baby can’t tell you when she isn’t feeling well or feels feverish, it helps to pay attention to her general behavior too. “When baby has a fever she will feed less and either sleep more or sleep less,” Altmann says. “She might be fussier or might not look right at you.”
Take all of these signs of fever in a newborn very seriously, because in a baby 3 months or younger, any sign of temperature could be a red flag. A potentially serious illness may be what causes baby fever, so you’ll want to see your pediatrician ASAP. Keep an eye out for the following signs of fever in a newborn:
- Baby feels warm. “If your baby is hotter than usual, that’s a big sign of fever,” McAllister says.
- There’s a change in behavior. Note how baby is behaving. Is something off from his usual temperament? Is he crying a lot or acting generally fussy? If so, this could be a sign of baby fever.
- Feeding has changed. If baby won’t take a bottle or breast, it could be the reaction to a spike in baby temperature.
- Sleeping has changed. Again, baby might be sleeping more—or less—than usual. Both are signs of potential temperature change.
How to Take Baby’s Temperature
Even with all the fancy forehead, ear and under-the-arm thermometers on the market—check out our comprehensive guide!—according to the experts, the gold standard for taking newborn temperature is to use a rectal thermometer. “I usually tell parents there are good forehead thermometers that are perfectly fine for screening a temperature,” Altmann says. “But if that thermometer shows that baby’s temperature is elevated and you call your pediatrician, he or she will still want you to do a rectal reading right away to get a definitive answer.” Look for a digital rectal thermometer with a wide base and a short, flexible tip which will help keep you from inserting it too far.
Don’t know how to take a baby’s temperature? Place baby on a changing table, add a little dab of petroleum jelly on the end of the thermometer and insert it gently about half an inch into baby’s bottom until it beeps. Then remove it carefully and take the reading.
According to the American Academy of Pediatrics, “a normal temperature for a child may range from 97 degrees Fahrenheit (F) to 100.4 degrees F,” with infants often registering slightly higher than older babies. Because there are several methods of taking newborn temperature, we’ve included a handy guide to show you the normal body temperature of babies whether you’re checking temperature in the ear, mouth, rectum or under the arm. You’ll want to consult this guide before reaching for an infant fever reducer, but regardless of the method, anything higher than 100.4 is considered a fever in babies.
Why Do Babies Get Fevers?
Fever in babies can sometimes seem to come out of nowhere, but, generally speaking, what causes baby fever tends to be very specific. Anything from a urinary tract infection, ear infection or another more generalized infection can be the cause. “A fever of any origin is a sign you need to take baby to the doctor,” McAllister says. “When they’re 3 months or younger, [infant fever is] considered a medical emergency.”
Sometimes, though, it could just be that baby fever is caused by overheating. “If baby is over bundled, that could cause him to feel warm and maybe even exhibit an elevated temperature,” Altmann says. “If a parent calls me and tells me her 2-month-old was swaddled, sleeping, has a temperature of 100.4° but otherwise seems fine, I will tell them to un-swaddle the baby and retake the temperature in 15 minutes. If it’s truly 100.4° 15 minutes later, then we need to do a work-up. If you un-swaddle the baby and the baby’s temperature is normal and he’s acting fine, I’ll suggest we keep an eye on it, but it’s not as urgent.”
Keep in mind that vaccines may sometimes cause a low-grade fever in babies. If baby is less than 3 months of age, it’s still a good idea to call your pediatrician if the baby fever after shots measures 100.4° or higher on a rectal thermometer. But if baby is 4 months or older, a fever of 100.4° to 102° after vaccines is nothing to be alarmed about, Altmann says. As long as baby is otherwise acting normal and eating well, you can use a fever medicine for baby, and he’ll likely be back on track pretty quickly. Of course, if baby isn’t acting like himself, having breathing problems or crying in pain associated with baby fever, when to call the doctor is sooner rather than later!
Do Babies Get Fevers From Teething?
A baby teething fever is a real thing, but you should keep in mind that the fever will be low grade. “Any fever over 100.4° F is a sign that your child is probably sick.” If the baby fever symptoms seem to be in line with those associated with teething, like drooling, swollen gums and chewing on her fingers, and it’s a low-grade fever, then teething is the likely culprit.
What to Do If Baby Has a Fever
Here are some things you can do if you find yourself up in the middle up the night wondering how to break a fever in a baby. Don’t discount home remedies for baby fever either, as they can be effective ways to reduce baby’s temperature.
- Give an infant fever reducer (if approved by a pediatrician). If baby is under 6 months with a fever, call your doctor immediately before giving fever medicine for baby like Tylenol. Your doctor is likely going to want to examine baby in person to figure out why he is sick and feverish. “For example, if it’s an ear infection, baby will need antibiotics,” McAllister says. Your pediatrician will also want to know exactly how much baby weighs at the time so he can prescribe the correct dosage if he recommends medicating with Tylenol. If baby is over 6 months, you can go ahead and give an infant fever reducer without consulting your doctor.
- Keep baby hydrated. When baby has a fever, keeping her hydrated with breast milk or formula is super important. You may want to offer extra breast- or bottle-feeding sessions. “Usually babies don’t need other fluids, but speak to your pediatrician to see if baby needs an electrolyte solution,” Altmann says.
- Consider a sponge bath. This is one of the most effective home remedies for baby fever. Rather than giving baby a full bath where she’s immersed in water, simply give baby a sponge bath to soothe her, dabbing a lukewarm washcloth on her forehead, neck and arms. “Make sure the water is lukewarm though,” Altmann says. “If the water is too cold it may cause baby to shiver, which could actually elevate the fever.”
Baby Fever: When to Call the Doctor
The AAP breaks down fever in babies by age and temperature. Follow these expert recommendations on exactly when you should bring a feverish baby to the doctor:
- Under 3 months: A newborn temperature of 100.4° Fahrenheit or higher must be checked out by a medical professional immediately since infection can spread more rapidly in an infant. Call your doctor at the first sign of fever. “Newborns don’t have the immunity yet that an older baby has so they can get very sick very quickly,” Altmann says.
- 3 to 6 months: When dealing with fever in babies, when to worry at this stage is at 102° F or higher. “Babies at this age are better able to deal with a fever,” McAllister says. Still, don’t self-medicate with Tylenol. Instead, call your doctor to discuss fever treatments. Also, if baby’s temperature lasts more than a few days or there are other concerning signs, like baby’s not drinking fluids, not acting like herself or is crying or throwing up, call your pediatrician immediately.
- 6+ months: If baby has a fever at this age, it may be a baby teething fever, or it could be due to an ear infection or a respiratory tract infection. And it’s okay to give Tylenol without consulting your doctor. However, if the baby fever continues or baby pulls at his ears, book a pediatrician appointment immediately. “At this age, we’re more concerned about how many days the fever has lasted, the other symptoms the baby has, whether he is coughing, throwing up, sleeping or drinking fluids,” Altmann says. “If the baby is acting fine, we suggest observing the temperature for a few days, but call if fever lasts longer than three or four days.”
FYI: No matter what age, call your pediatrician immediately if baby is ever weak or feels limp, there’s any change in her skin color or her breathing is either shallow, slower or faster than normal, McAllister says.
Experts: Tanya Altmann, MD, FAAP, a Los Angeles–based pediatrician and assistant clinical professor at Mattel Children’s Hospital at UCLA; Rallie McAllister, MD, MPH, a family physician in Lexington, Kentucky, and coauthor of The Mommy MD Guide to Your Baby’s First Year.