A fever in a child is a temperature of 100.4°F (38°C) or higher when measured rectally, in the ear, or on the forehead. It’s the body’s natural response to infection, and in most cases, the best thing you can do is keep your child comfortable, hydrated, and monitored while their immune system does its job. That said, a few situations call for immediate medical attention, and age matters enormously in determining how urgent a fever is.
How to Tell If It’s Actually a Fever
The number that counts as a fever depends on where you take the temperature. A rectal, ear, or forehead reading of 100.4°F (38°C) or higher is a fever. An oral reading of 100°F (37.8°C) or higher also qualifies. Armpit temperatures register lower, so anything at or above 99°F (37.2°C) suggests a fever, but armpit readings are the least reliable. If an armpit reading seems off, confirm it with another method.
For babies under 3 months, a rectal thermometer gives the most accurate result and is the one pediatricians want you to use. For toddlers and older children, ear and forehead thermometers are faster and easier.
Why Children Get Fevers
Fever isn’t the illness itself. It’s a sign that your child’s immune system has detected something and is ramping up its defense. When body temperature rises, immune cells become more active. Research has shown that at around 102.2°F (39°C), the T cells responsible for fighting infections multiply faster and work harder, while the cells that normally dial the immune response down become less active. In other words, a moderate fever creates conditions that help the body clear an infection more efficiently.
This is why doctors generally don’t recommend treating a fever purely to get the number down. The goal is comfort, not a specific temperature on the thermometer.
Comfort Measures That Help
Dress your child in lightweight clothing and use a light blanket if they’re chilly. Heavy blankets and bundling can trap heat and push the temperature higher. Keep the room at a comfortable temperature rather than cranking up the heat or blasting air conditioning.
A lukewarm sponge bath can bring some relief. Use water between 90°F and 95°F (32–35°C). Never use cold water, ice, or rubbing alcohol. Cold water causes shivering, which actually raises the body’s core temperature, and rubbing alcohol can be absorbed through the skin and is toxic to children.
Encourage rest, but don’t force a child to stay in bed if they’re feeling well enough to move around. Many kids with fevers of 101–102°F still want to play, and that’s fine. Their energy level tells you more about how sick they are than the thermometer does.
Keeping Your Child Hydrated
Fever increases fluid loss through the skin, so children need to drink more than usual. Water, diluted juice, broth, and popsicles all count. For children who are also vomiting or have diarrhea, an oral rehydration solution replaces lost electrolytes more effectively than water alone. Avoid sodas, energy drinks, and anything high in caffeine or sugar, which can worsen dehydration.
Watch for signs that your child is getting dehydrated. In infants, red flags include no wet diapers for three hours, no tears when crying, a dry mouth, and a sunken soft spot on top of the head. In older children, look for infrequent urination, sunken eyes, dry lips and tongue, and skin that stays tented when you gently pinch it instead of flattening back right away. A child who seems unusually cranky or has no energy may also be dehydrated.
When to Use Fever-Reducing Medication
Acetaminophen and ibuprofen are the two options for bringing down a child’s fever. You don’t need to give either one if your child seems comfortable. These medications are for relieving discomfort, not for hitting a target number.
Acetaminophen can be given every 4 to 6 hours, up to 5 doses in 24 hours. It should not be given to infants under 8 weeks old. Ibuprofen can be given every 6 to 8 hours, up to 4 doses in 24 hours, but should not be given to babies under 6 months old unless a doctor specifically advises it. Both medications are dosed by weight, not age, so check the label carefully or call your pediatrician’s office if you’re unsure about the right amount.
Never give aspirin to a child or teenager. Aspirin use during a viral illness is linked to Reye’s syndrome, a rare but serious condition that causes dangerous swelling in the liver and brain. It can lead to seizures, loss of consciousness, and in some cases, death. This includes any over-the-counter product that contains aspirin as an ingredient, so read labels carefully.
Fevers in Babies Under 3 Months
A fever in a very young infant is treated differently than in an older child. If your baby is under 3 months old and has a rectal temperature of 100.4°F or higher, contact your pediatrician right away or go to the emergency department. Even if the baby looks well, young infants can have serious bacterial infections without obvious symptoms, and doctors will likely want to evaluate them promptly. Do not give fever-reducing medication to a newborn and wait to see what happens. The fever itself is the signal to seek care.
What to Do If Your Child Has a Seizure
Febrile seizures happen in about 2–5% of children, most commonly between ages 6 months and 5 years, with the highest risk between ages 1 and 3. They’re triggered by the rapid rise in temperature rather than how high the fever gets, and they’re almost always harmless despite being terrifying to watch.
If your child has a seizure during a fever, note the time it starts. Place your child on the floor on their side to prevent choking. Do not hold them down or try to put anything in their mouth. If the seizure lasts longer than 5 minutes, call 911. If it stops within 5 minutes but your child doesn’t seem to recover quickly, also call for help. Any first-time febrile seizure should be evaluated by a doctor, even if it was brief and the child seems fine afterward.
Simple febrile seizures, the most common type, last a few seconds to 15 minutes and happen only once within a 24-hour period. They don’t cause brain damage or increase the risk of epilepsy. Complex febrile seizures, which last longer than 15 minutes, recur within 24 hours, or affect only one side of the body, need more thorough medical evaluation.
Signs That Need Emergency Attention
Most fevers resolve on their own within a few days. But certain symptoms alongside a fever signal something more serious. Go to the emergency department or call 911 if your child has a fever with any of the following:
- Extreme drowsiness or difficulty waking up
- A stiff neck
- A new rash
- Trouble breathing
- Inconsolable crying
- Excessive drooling or difficulty swallowing
- Abdominal pain or tenderness
- Altered speech or trouble walking
- Blue lips, tongue, or nails
Outside of emergency symptoms, call your pediatrician if a fever lasts more than 3 days in a child of any age, if your child shows signs of dehydration, or if the fever keeps returning after going away. Trust your instincts as a parent. If something about your child’s behavior feels wrong, even if you can’t pinpoint exactly what, that’s a valid reason to call.