A fever in a baby is the body’s natural defense against infection, not a disease itself. Your main goal isn’t to hit a specific number on the thermometer but to keep your baby comfortable and hydrated while their immune system does its job. That said, there are safe, effective ways to bring a fever down when your baby is miserable, and some important age-based rules to follow.
What Counts as a Fever
For babies, a rectal thermometer gives the most accurate reading. A rectal temperature of 100.4°F (38°C) or higher is a fever. If you’re using an armpit thermometer, the threshold is lower: 99°F (37.2°C) or higher. Ear and temporal artery thermometers also register a fever at 100.4°F, but rectal remains the gold standard for infants under three months because even small inaccuracies matter at that age.
Age Matters: Under 3 Months Is Different
If your baby is younger than three months and has a rectal temperature of 100.4°F or higher, contact your pediatrician right away or go to the emergency room. Do not wait to see if the fever comes down on its own, and do not give fever-reducing medication first. Young infants have immature immune systems, and a fever at this age can signal a serious bacterial infection that needs prompt evaluation.
For babies three to six months old, call your doctor if the temperature reaches 101°F (38.3°C) or higher, or if it’s below that but your baby seems unusually irritable, limp, or hard to wake. For babies six months to two years, a fever above 101°F that lasts more than a day without other symptoms also warrants a call.
Fever-Reducing Medication
Acetaminophen (Tylenol) is the go-to option for babies two months and older. It can be given every four hours as needed. The children’s liquid suspension contains 160 mg per 5 ml, and dosing is based on your baby’s weight:
- 6 to 11 lbs: 1.25 ml
- 12 to 17 lbs: 2.5 ml
- 18 to 23 lbs: 3.75 ml
- 24 to 35 lbs: 5 ml
Ibuprofen (Motrin) is an option for babies six months and older. It can be given every six hours. Infant concentrated drops (50 mg per 1.25 ml) and children’s liquid (100 mg per 5 ml) have different concentrations, so always check which product you have before dosing. For a baby 12 to 17 lbs, the dose is 1.25 ml of the infant drops or 2.5 ml of the children’s liquid. For 18 to 23 lbs, it’s 1.875 ml of the drops or 3.75 ml of the liquid. Do not give ibuprofen to any baby under six months.
Never give aspirin to a child or teenager. Aspirin use during a viral illness is linked to Reye’s syndrome, a rare but potentially life-threatening condition that causes swelling in the liver and brain. This risk is highest in children recovering from the flu or chickenpox.
Keep Your Baby Cool, Not Cold
Overdressing a feverish baby traps heat and can push the temperature higher. Dress your baby in a single lightweight layer, like a short-sleeve bodysuit. Remove hats indoors, since babies release a significant amount of heat through their heads. If you’re using a sleep sack, choose the lightest tog rating you have and don’t layer blankets on top. Air trapped between layers acts as insulation and increases overheating risk.
Keep the room between 60°F and 68°F (16 to 20°C). If the room is warmer than 68°F, a single layer or even just a diaper is fine. To check whether your baby is too warm, feel the skin on their chest or the back of their neck. Hands and feet tend to run cool naturally, so they’re not a reliable gauge. If the chest feels hot or sweaty, remove a layer.
A lukewarm sponge bath can also help bring a fever down. Use water that feels comfortable to the inside of your wrist. Avoid cold water or ice baths, which can cause shivering. Shivering actually raises the body’s core temperature, working against what you’re trying to do.
Hydration Is Critical
Fever increases fluid loss through sweating and faster breathing. For babies under six months, offer breast milk or formula more frequently than usual. For older babies, you can also offer small sips of water or an electrolyte solution between feedings. The goal is to maintain at least six to eight wet diapers in a 24-hour period. Fewer than three or four wet diapers a day signals dehydration.
Watch for other dehydration signs: crying with fewer tears than normal, a dry mouth, or a sunken soft spot on the top of your baby’s head. If you notice any of these, contact your pediatrician promptly.
What to Do if Your Baby Has a Seizure
Febrile seizures, triggered by a rapid rise in body temperature, affect children between six months and five years old and are most common in the first three years of life. They look frightening but typically last only a few minutes. A simple febrile seizure is under 15 minutes long and doesn’t recur within 24 hours.
If your baby has a seizure, place them on a flat surface on their side. Don’t put anything in their mouth or try to restrain their movements. Time the seizure if you can. Once it’s over, your baby may seem groggy or confused for a short period. Even if the seizure stops quickly on its own, call your doctor or visit the emergency room after a first-time febrile seizure. They’ll want to confirm it was caused by the fever and not something else.
Signs That Need Immediate Attention
Beyond the age-based temperature thresholds above, certain symptoms alongside a fever call for emergency care regardless of your baby’s age:
- Difficulty breathing or labored, rapid breaths
- Skin or lips that look blue, purple, or gray
- Unusual sleepiness where your baby is hard to wake or seems floppy
- A rash that appears suddenly, blisters, or looks infected
- Persistent pain or fussiness that worsens or doesn’t respond to comfort
- Loss of consciousness or your baby seeming withdrawn or less alert than normal
A fever that returns repeatedly over several days, even if it responds to medication each time, is also worth discussing with your pediatrician. The fever itself is rarely dangerous, but the pattern can help your doctor identify whether something beyond a routine virus is going on.