A baby’s fever usually responds well to a combination of the right medication, light clothing, and plenty of fluids. A rectal temperature of 100.4°F (38°C) or higher counts as a fever in infants. Most fevers are the body’s normal response to infection and resolve within a few days, but age matters: any fever in a baby younger than 3 months old requires an immediate call to your pediatrician, no matter how mild the number looks.
How to Tell if Your Baby Has a Fever
Rectal thermometers are the gold standard for babies and give the most accurate reading. A rectal, ear, or temporal artery temperature of 100.4°F or higher confirms a fever. If you’re using an oral thermometer (for older toddlers), the threshold is 100°F. An armpit reading of 99°F or higher also suggests a fever, though armpit readings tend to be less reliable.
Touch alone isn’t enough. A baby can feel warm from crying, being overdressed, or sitting in a warm room. If your baby seems off, take an actual reading before deciding on next steps.
Age-Based Rules That Override Everything Else
For babies under 3 months old, call your pediatrician for any fever of 100.4°F or above. At this age, even a low-grade fever can signal a serious bacterial infection, and doctors will want to evaluate the baby quickly rather than wait.
Babies between 3 and 6 months old need a call to the doctor if their rectal temperature climbs above 102°F, or if they seem unusually irritable, sluggish, or uncomfortable even with a lower temperature. After 6 months, you generally have more room to manage the fever at home, but trust your instincts. A baby who looks sick probably needs to be seen.
Fever-Reducing Medication
Acetaminophen (Tylenol) is the go-to option for young babies. You can give it every 4 to 6 hours as needed, up to 5 times in 24 hours. Always dose by your baby’s weight, not their age, since weight-based dosing is more accurate. Do not give acetaminophen to infants under 8 weeks old without your doctor’s guidance.
Ibuprofen (Advil, Motrin) is an option once your baby is at least 6 months old. It’s given every 6 to 8 hours, up to 4 times in a day, and works best when taken with a little food or milk to avoid stomach upset. The FDA has not approved ibuprofen for use in babies under 6 months, so don’t reach for it early.
Never give aspirin to a child or teenager. Aspirin use during a viral illness like the flu or chickenpox has been linked to Reye’s syndrome, a rare but serious condition that causes dangerous swelling in the liver and brain. This risk is why children’s fever products are exclusively acetaminophen or ibuprofen based.
Cooling Strategies That Actually Help
Strip your baby down to a single light layer of clothing. Infants can’t regulate their own temperature well, so extra blankets or layers trap heat and make it harder for the fever to come down. At night, one lightweight blanket over a single layer of clothes is enough. Keep the room at a comfortable temperature rather than cranking up the heat.
A lukewarm sponge bath can help bring the temperature down, but it works best when combined with medication. On its own, the temperature tends to bounce right back up once the bath is over. Use water that feels comfortably warm to the inside of your wrist. Cold baths, ice packs, and alcohol rubs should all be avoided. They cause shivering, which actually raises the body’s core temperature and makes the situation worse.
Keeping Your Baby Hydrated
Fever increases fluid loss, so offer breast milk or formula more frequently than usual. For babies over 6 months who are eating solids, small sips of water between feedings help too. The goal is to keep your baby producing a normal number of wet diapers.
Watch for these signs of dehydration:
- Fewer wet diapers than usual over the course of 24 hours
- A sunken soft spot on the top of the head
- Sunken eyes or few to no tears when crying
- Unusual drowsiness or irritability that doesn’t improve
If you notice any of these signs alongside a fever, contact your pediatrician promptly. Dehydration in a small baby can escalate quickly.
Warning Signs That Need Immediate Attention
Most fevers are harmless and resolve on their own, but certain symptoms alongside a fever signal something more serious. Seek emergency care if your baby has difficulty breathing, persistent vomiting, a stiff neck, a rash, or a seizure. If your baby seems listless, makes poor eye contact, or is difficult to wake, that also warrants urgent evaluation.
What to Know About Febrile Seizures
Some children between 6 months and 5 years old experience seizures triggered by fever. During a febrile seizure, a child typically shakes all over, stiffens, and loses consciousness. It looks terrifying, but most febrile seizures are brief, lasting anywhere from a few seconds to 15 minutes, and don’t cause lasting harm.
If it happens, lay your child on a safe surface away from hard objects. Don’t put anything in their mouth or try to restrain them. Time the seizure. If it lasts longer than 5 minutes, or is accompanied by vomiting, a stiff neck, breathing problems, or extreme sleepiness afterward, call 911. Even if the seizure is short and your child recovers quickly, call your pediatrician after the first one so they can evaluate your child and rule out other causes.
Febrile seizures are not caused by how high the fever gets. They can happen even with relatively low fevers, and giving fever reducers proactively does not reliably prevent them.