The fastest way to bring down a baby’s fever is a dose of infant acetaminophen (if your baby is old enough), light clothing, extra fluids, and a comfortable room temperature. A fever in a baby is any rectal temperature at or above 100.4°F (38°C). Before you do anything else, your baby’s age matters enormously: any fever in a baby under 3 months old requires an immediate call to your pediatrician, regardless of how mild it seems.
Check Your Baby’s Age First
Age changes everything about how a fever in a baby should be handled. For infants younger than 3 months, a fever of 100.4°F or higher is treated as urgent. Their immune systems are still developing, and a fever at this age can signal a serious infection that’s hard to detect from symptoms alone. Call your pediatrician or go to the emergency room right away. Do not give any medication to a baby this young without being told to do so by a doctor.
For babies 3 to 6 months old, call your pediatrician if the temperature reaches 100.4°F or if your baby seems unusually sick, fussy, or sleepy even with a lower reading. For babies 6 to 24 months old, a fever above 100.4°F that lasts more than one day warrants a call. Any fever lasting more than three days at any age should be evaluated.
Fever-Reducing Medication by Age
Infant acetaminophen (commonly sold as Tylenol) is the go-to fever reducer, but it should not be given to babies under 2 years old without guidance from a doctor. If your pediatrician has approved it, dose by your baby’s weight, not age. The liquid form comes as 160 mg per 5 mL. You can give a dose every 4 hours as needed, but never more than 5 doses in 24 hours.
Ibuprofen (infant Motrin or Advil) is off-limits for babies under 6 months. It has not been found safe for that age group. Once your baby is 6 months or older, ibuprofen becomes an option, again dosed by weight. If you’re unsure about the right amount, call your pediatrician’s office. Many have nurses who can walk you through dosing over the phone in minutes.
Never give aspirin to a baby, child, or teenager. Aspirin is linked to Reye’s syndrome, a rare but serious condition that causes swelling in the liver and brain. This applies to plain aspirin and any medicine that contains it.
Can You Alternate Acetaminophen and Ibuprofen?
Alternating the two medications can lower a fever more effectively than either one alone, but it also raises the risk of accidentally giving the wrong dose or dosing too frequently. The American Academy of Pediatrics does not recommend routinely alternating them unless a pediatrician has specifically instructed you to do so and given you a written schedule. A single medication, dosed correctly, is safer for most families.
Comfort Measures That Actually Help
Medication works from the inside. These steps help from the outside, and they make a real difference when used together.
Keep the room cool, not cold. Aim for 68 to 72°F (20 to 22°C). A slightly cooler room helps your baby’s body release excess heat naturally. If your home runs warmer than 77°F, a diaper and a thin cotton onesie may be all your baby needs.
Dress in one light layer. A single layer of breathable cotton, like a onesie or light pajamas, is ideal. If you use a sleep sack, choose one with a low warmth rating (0.5 TOG or lower). Do not bundle your baby in extra blankets or layers. This traps heat and can push the fever higher. At the same time, don’t strip your baby down to just a diaper if the room is cool. Shivering is the body’s way of generating heat, which works against you.
Try a lukewarm sponge bath. Use water between 90°F and 95°F (32 to 35°C), which feels comfortably warm to your inner wrist. Gently sponge your baby’s skin and let the water evaporate, which draws heat away. Never use cold water, ice, or rubbing alcohol. Cold water causes shivering, and alcohol can be absorbed through the skin and is dangerous for babies.
Push Fluids to Prevent Dehydration
Fever speeds up fluid loss. Babies dehydrate faster than adults, and a dehydrated baby will feel worse and recover more slowly. If you’re breastfeeding or formula feeding, offer smaller, more frequent feeds. For babies over 6 months who are eating solids, small sips of water between feedings can help.
Watch the diapers. Six to eight wet diapers a day is normal. Fewer than three or four wet diapers in a day is a sign of dehydration. Other warning signs include a sunken soft spot (the fontanelle on top of the head), no tears when crying, extreme sleepiness, feeding less than normal, and unusual irritability or listlessness. If you see these signs, call your pediatrician promptly.
How to Take an Accurate Temperature
For babies under 3 months, a rectal thermometer gives the most accurate reading and is the one pediatricians rely on. A rectal temperature of 100.4°F (38°C) or higher is a fever. Temporal artery (forehead) and ear thermometers use the same threshold. Armpit readings run lower, so 99°F (37.2°C) or above in the armpit counts as a fever. If you get a concerning armpit reading, confirm it rectally before calling your doctor.
Signs That Need Emergency Attention
Most fevers in babies are caused by common viral infections and resolve within a few days. But certain symptoms alongside a fever signal something more serious. Get immediate care if your baby shows any of the following:
- Skin or lips that look blue, purple, or gray
- Extreme floppiness or difficulty waking up
- Repeated vomiting
- A rash that appears suddenly, blisters, or looks infected
- Acting strangely or seeming much less alert than usual
- Pain or fussiness that keeps getting worse and won’t stop
Trust your instincts. If something feels off about how your baby looks or acts, even if the fever number doesn’t seem that high, that’s reason enough to call.