A baby has a fever when their rectal temperature reaches 100.4°F (38°C) or higher. Most fevers in infants are caused by common viral infections and resolve on their own within a few days, but your job is to keep your baby comfortable, well-hydrated, and watched for warning signs. What you need to do depends largely on your baby’s age.
Age Matters More Than the Number
For babies under 3 months old, any rectal temperature of 100.4°F or higher needs immediate medical attention. At this age, a baby’s immune system is still immature, and fever can be the only sign of a serious infection. Don’t give medication or try to treat the fever at home first. Go straight to your pediatrician or emergency department.
For babies 3 to 6 months old, a temperature up to 101°F (38.3°C) doesn’t automatically require a visit, but watch closely. If your baby seems unusually irritable, sluggish, or uncomfortable, or if the temperature climbs above 101°F, call your doctor. For babies 6 to 24 months, a fever above 101°F that lasts longer than a full day without other symptoms also warrants a call. In all these cases, how your baby looks and acts matters as much as the thermometer reading.
Keeping Your Baby Hydrated
Fever speeds up fluid loss, and babies dehydrate faster than older children. Infants under 6 months get all the fluid they need from breast milk or formula, so the goal is simply to offer feeds more frequently than usual. You don’t need to give water to a baby this young. Babies 7 to 12 months old can have small sips of water alongside their regular milk and solid foods, aiming for roughly 0.8 liters of total fluid per day from all sources.
Watch for signs that your baby isn’t getting enough fluid. Mild dehydration shows up as fewer wet diapers than normal. Moderate dehydration adds a dry mouth and lips, darker urine, cool hands and feet, and a quieter-than-usual baby. Severe dehydration is an emergency: look for sunken eyes, cold or mottled (patchy, bluish-red) skin, extreme sleepiness, or very little urine output. If you see those signs, get medical help right away.
Medication: What’s Safe and What’s Not
Acetaminophen (Tylenol) is the main fever-reducing option for babies, but for children under 2 years old, check with your doctor before giving it. Your doctor will base the dose on your baby’s current weight, not age. The liquid form comes in a concentration of 160 mg per 5 mL, and doses can be repeated every 4 hours if needed, with a maximum of 5 doses in 24 hours. Ibuprofen (Advil, Motrin) is not recommended for babies under 6 months old.
Never give aspirin to a baby, child, or teenager. Aspirin given during a viral illness has been linked to Reye’s syndrome, a rare but dangerous condition where the liver swells, blood sugar drops, and the brain can swell enough to cause seizures or loss of consciousness. Also avoid combination cold-and-flu medicines for children under 6. Stick to a single-ingredient product and confirm the dose with your pediatrician.
Comfort Measures That Actually Help
A lukewarm sponge bath can bring a fever down temporarily, but it works best when paired with fever-reducing medication. Without medicine, the temperature tends to bounce right back up after the bath. Use water that feels comfortably warm to the inside of your wrist. Never use cold water, ice, or rubbing alcohol. These cause shivering, which actually drives the body’s core temperature higher.
Dress your baby in a single light layer. The instinct to pile on blankets is counterproductive because trapping heat prevents the body from cooling naturally. Keep the room between 68°F and 72°F. To check whether your baby is overheating, feel their chest or back rather than their hands or feet. Sweating, flushed cheeks, or skin that feels hot to the touch on the torso means you should remove a layer. During sleep, skip loose blankets entirely, both for temperature regulation and to reduce suffocation risk.
Signs That Need Emergency Care
Beyond the age-based guidelines above, certain symptoms alongside a fever mean you should seek care immediately:
- Inconsolable crying that doesn’t improve with holding or feeding
- Extreme sleepiness or limpness, where your baby is hard to wake or seems unresponsive
- Difficulty breathing, including flaring nostrils, fast breathing, or the skin pulling in between the ribs
- A rash of small purple or red dots that don’t fade when you press on them (called petechiae), which can signal a serious blood infection
- A baby who still looks sick after the fever comes down. A child who perks up once the temperature drops is reassuring. One who remains listless even after the fever breaks needs prompt evaluation.
Any new symptoms that develop during an illness, or a fever that climbs higher than before, are also reasons to call your doctor or go in.
What to Know About Febrile Seizures
About 3% of healthy children experience a febrile seizure, typically between the ages of 6 months and 6 years. These seizures are triggered by the rapid rise in temperature, not by how high the fever gets, which means they often happen before you even realize your baby has a fever. During a seizure, lay your baby on their side on a flat surface, keep the area clear, and time it. Most febrile seizures stop on their own within a couple of minutes and don’t cause lasting harm.
A seizure lasting longer than 5 minutes is a medical emergency. Call emergency services. You should also seek medical evaluation if the seizure affects only one side of the body, if your baby has more than one seizure within 24 hours, or if this is your baby’s first febrile seizure (your doctor will want to examine them afterward to rule out other causes).