A 6-month-old has a fever when their temperature reaches 100.4°F (38°C) or higher, measured rectally. Most fevers at this age are caused by common viral infections and resolve on their own within a few days. Your main jobs are to keep your baby comfortable, watch for warning signs, and make sure they stay hydrated.
Why Babies Get Fevers
Fever is not an illness itself. It’s your baby’s immune system actively fighting off an infection. A higher body temperature slows the growth and reproduction of viruses and bacteria while boosting the immune response. Some evidence suggests fever actually helps the body recover more quickly from viral infections. So while it’s unsettling to feel your baby burning up, the fever is doing useful work.
At six months, babies are losing the protective antibodies they got from their mother during pregnancy, which means they start catching more bugs. Teething can also cause a mild temperature rise, though it rarely pushes above 100.4°F.
How to Take an Accurate Temperature
A rectal thermometer gives the most reliable reading for a baby this age. Forehead (temporal artery) and ear thermometers are reasonable alternatives, but if you get a borderline reading with one of those, confirm it rectally. Forehead strip thermometers and “feeling warm to the touch” are not accurate enough to guide decisions.
To take a rectal temperature, apply a small amount of petroleum jelly to the tip, gently insert it about half an inch, and hold it in place until it beeps. Write down the reading and the time so you can track whether the fever is rising, falling, or holding steady.
Keeping Your Baby Comfortable
Dress your baby in a single light layer of clothing. Bundling them up can trap heat and push the temperature higher. Keep the room at a comfortable temperature, not cold. A lukewarm (not cold) sponge bath can help bring mild relief, but stop if your baby starts shivering, since shivering actually raises body temperature.
Offer frequent breastfeeds or formula. Babies with fevers lose fluid faster through sweating and rapid breathing, so more frequent, smaller feedings work better than trying to get them to take a large one. If your baby has started solids, you can also offer small sips of water between feeds.
When Fever Medicine Is Appropriate
Acetaminophen (Tylenol) is the go-to fever reducer for babies under six months, but at exactly six months, ibuprofen (Motrin, Advil) also becomes an option. Ibuprofen is not approved for babies younger than six months.
For both medications, dosing is based on your baby’s weight, not their age. The liquid form of acetaminophen typically comes as 160 mg per 5 mL. For children under two, check with your pediatrician to confirm the correct dose before giving either medication. Ibuprofen can be repeated every six to eight hours if needed, while acetaminophen can be given every four to six hours. Never give aspirin to a baby or child.
You don’t need to treat every fever with medicine. If your baby is sleeping comfortably or acting fairly normal, it’s fine to let the fever do its job and skip the medication. Fever reducers are most helpful when your baby is clearly miserable, can’t sleep, or won’t eat.
Signs of Dehydration to Watch For
Dehydration is the most common complication of fever in babies, and it can develop quickly. Watch for these signs:
- Fewer wet diapers than usual or no wet diaper for eight hours
- No tears when crying
- Sunken soft spot on the top of the head
- Sunken eyes or dry mouth
- Unusual drowsiness or irritability
If you notice any of these, contact your pediatrician right away. Keeping a simple log of feeding times and diaper changes during a fever makes it much easier to spot a pattern of decreasing output.
When to Call Your Pediatrician
For a baby between 6 and 24 months old, call your doctor if the fever above 100.4°F lasts longer than one day. Also call if your baby:
- Misses two or more feedings in a row or eats poorly
- Is sleeping much more than usual or is hard to wake up
- Seems floppy, unusually irritable, or impossible to comfort
- Is vomiting after feedings or hasn’t kept liquids down for eight hours
- Has a cough with fast or labored breathing
- Develops a rash that appears quickly, blisters, or looks infected
- Has ear pain or pulls at their ears repeatedly
- Has a fever of 102.2°F (39°C) or higher
- Has fevers that keep coming and going over a week or more
If your baby recently had an immunization and develops a low fever, that’s a common and expected reaction. Still, let your pediatrician know if the fever climbs above 102°F or if your baby seems unusually distressed.
When to Go to the Emergency Room
Some symptoms alongside a fever require immediate care. Call 911 or go to the ER if your baby:
- Has a seizure (rhythmic jerking or sudden stiffness)
- Cannot be awakened or seems confused
- Has difficulty breathing even after you’ve cleared their nose
- Has blue or gray lips, tongue, or fingernails
- Has a stiff neck or refuses to move an arm or leg
- Develops new bruises or a purple/red rash that doesn’t fade when you press on it
- Is crying inconsolably and cannot be calmed
One important detail: if you give your baby a fever reducer and the temperature drops but your baby still doesn’t act more alert or comfortable, that’s a reason to seek care. In most viral fevers, babies perk up noticeably once the temperature comes down. A baby who stays listless even after medication needs medical evaluation.
What to Expect Over the Next Few Days
Most viral fevers in babies peak within the first 24 to 48 hours and then gradually come down over three to five days. It’s normal for the temperature to spike higher in the late afternoon and evening and dip lower in the morning. This pattern doesn’t mean your baby is getting worse.
During recovery, your baby may be fussier than usual, sleep more, and eat less. As long as they’re still taking some fluids, producing wet diapers, and gradually improving, you’re on the right track. The fever itself, even if it looks high, matters less than how your baby is acting. A baby with a 103°F fever who is still making eye contact, responding to you, and taking fluids is generally in better shape than a baby with a 101°F fever who is limp and unresponsive.