What temperature counts as a fever in babies?

A fever in babies is defined as a rectal temperature of 100.4°F (38°C) or higher. Rectal measurement is the gold standard for infants under 3 months because it is the most accurate. Axillary (armpit) readings run about 0.5–1°F lower and are less reliable for clinical decisions.

When should I take my baby to the ER for a fever?

Go to the ER immediately if your baby is under 3 months old with any fever of 100.4°F (38°C) or higher, or if your baby of any age shows: a stiff neck, a purple or red non-blanching (petechiae) rash, difficulty breathing, extreme difficulty waking, a bulging fontanelle (soft spot), or a seizure.

What fever medications are safe for babies?

Acetaminophen (paracetamol) is safe from birth and is dosed at 10–15 mg per kilogram of body weight every 4–6 hours. Ibuprofen is safe only from 6 months of age, dosed at 5–10 mg/kg every 6–8 hours. Never give aspirin to a child or teenager due to the risk of Reye's syndrome. Never use combination cold-and-flu products that already contain a fever reducer.

What home cooling measures work for a baby with fever?

Dress your baby in a single light layer and keep the room comfortably cool. Offer extra feeds — breast milk, formula, or water for babies over 6 months — to prevent dehydration. A lukewarm (not cold) bath can briefly lower temperature. Do not use alcohol rubs or ice packs, as both can be dangerous for infants.

Can teething cause a fever?

Teething may cause a very slight rise in gum temperature, but research does not support it as a cause of true fever (100.4°F / 38°C or above). If your teething baby has a genuine fever, look for another cause and contact your doctor if the fever meets the call-doctor thresholds.

Are febrile seizures dangerous?

Febrile seizures are frightening to witness but are rarely dangerous. They affect roughly 2–5% of children under age 5 and typically last under 5 minutes. A simple febrile seizure does not cause brain damage or lead to epilepsy. However, any seizure in an infant should be evaluated by a doctor, and you should call 911 if it lasts more than 5 minutes or your child does not return to normal afterward.

Guides · Health

Baby Fever Guide: When to Call the Doctor (AAP Guidelines)

A fever is one of the most common reasons parents call their pediatrician — and one of the most misunderstood. This guide walks you through the American Academy of Pediatrics (AAP) thresholds by age, the ER warning signs you should never ignore, safe medication dosing, and the home care steps that actually work.

What is a fever? The 100.4°F / 38°C threshold

A fever is not a disease — it is a sign that the immune system is responding to infection or illness. The universally accepted threshold is a rectal temperature of 100.4°F (38°C) or higher. Any reading below this is not a fever, even if your baby feels warm to the touch.

The measuring method matters more than most parents realise:

Rectal (gold standard): The most accurate method for infants under 3 months. Insert a lubricated digital thermometer about half an inch into the rectum. A reading of 100.4°F (38°C) or above is a fever.
Temporal artery (forehead): Convenient and reasonably accurate for children over 3 months when used correctly. Hold the thermometer flat to the forehead and sweep from the centre to the hairline behind the ear.
Axillary (armpit): Easy but least reliable — typically reads 0.5–1°F (0.3–0.6°C) lower than true core temperature. Useful for quick screening but confirm a high reading rectally in young infants.
Tympanic (ear): Not recommended under 6 months because the ear canal is too narrow for accurate placement.
Oral: Not practical before age 4–5 years.

A temperature of 99°F (37.2°C) measured under the arm is not a fever. A temperature of 101°F (38.3°C) measured rectally is. Always note the method when you record or report a temperature so your doctor can interpret it correctly.

AAP call-doctor rules by age

The AAP has clear age-based guidance because the immune system matures over the first year of life, and fever in a very young infant can signal a serious infection that needs urgent evaluation.

Under 3 months (0–12 weeks) — go to the ER or call your doctor immediately: Any rectal fever of 100.4°F (38°C) or above in a newborn or young infant requires same-day evaluation, even if your baby seems well. At this age, the body cannot reliably contain bacterial infections, and serious illness can progress very quickly.
3–6 months — call your doctor the same day: A rectal temperature above 38.9°C (102°F) warrants a call to your pediatrician. If your baby is acting unusually ill, not feeding, or you are worried for any reason, do not wait.
6 months and older — monitor and call if high or prolonged: A temperature above 39.4°C (103°F), or any fever that lasts more than two to three days, or that comes with other concerning symptoms, warrants a call. For a well-appearing baby with a lower fever who is eating and playing normally, watchful waiting with comfort measures is usually appropriate.

These thresholds assume a baby who has received their routine vaccinations. Premature infants or babies with underlying medical conditions may have lower thresholds — ask your pediatrician what applies to your child.

Go to the ER immediately if your baby shows these signs

Regardless of age or the number on the thermometer, certain signs mean you should go to the emergency room or call emergency services without delay:

Stiff neck: Resistance when gently moving the head forward can indicate meningitis.
Petechiae or purpura rash: Small, flat red or purple spots that do not turn white (blanch) when you press on them. This can be a sign of a serious bacterial infection such as meningococcal disease. Press a glass against the spots — if they remain visible through the glass, go to the ER immediately.
Difficulty breathing: Rapid breathing, grunting, flaring nostrils, or the skin pulling in between or below the ribs with each breath.
Won't wake or extremely difficult to rouse: A baby who cannot be woken to feed or who is unusually limp and unresponsive needs urgent assessment.
Bulging fontanelle: The soft spot on top of the head should be flat or slightly sunken. A bulging fontanelle when your baby is calm and upright can signal increased pressure inside the skull.
Seizure: Any convulsion in an infant should be evaluated. Call emergency services if the seizure lasts more than 5 minutes or the child does not return to their normal self within 30 minutes.
Severe dehydration: No wet nappy in 8 hours, no tears when crying, dry mouth, and sunken eyes are signs your baby needs IV fluids.

Trust your instincts. If something about your baby's appearance simply does not feel right, seek help even if they do not tick the boxes above.

Safe fever medications: acetaminophen and ibuprofen

Fever-reducing medications do not treat the underlying infection — they make your baby more comfortable while the immune system does its job. There are two safe options, and the rules around them are strict.

Acetaminophen (paracetamol / Tylenol, Calpol, etc.): Safe from birth. The correct dose is 10–15 mg per kilogram of body weight, given every 4–6 hours as needed, up to five doses in 24 hours. Always dose by weight, not by age — the printed age brackets on packaging are approximations that can result in under- or over-dosing.
Ibuprofen (Advil, Motrin, Nurofen, etc.): Safe only from 6 months of age. The correct dose is 5–10 mg per kilogram of body weight, given every 6–8 hours as needed, up to four doses in 24 hours. It should not be given if your baby is dehydrated or vomiting repeatedly, as it can affect kidney function.

Never give aspirin to a child or teenager with a viral illness. Aspirin use in this context is linked to Reye's syndrome, a rare but potentially fatal condition causing liver and brain damage.

Never combine or alternate without a doctor's guidance. Alternating acetaminophen and ibuprofen is sometimes recommended by pediatricians for high, persistent fever, but it increases the risk of dosing errors. If your doctor has not specifically advised this, stick to one medication.

Do not use combination products (cold-and-flu preparations, decongestant syrups) that already contain acetaminophen or ibuprofen — you may inadvertently double-dose.

Always use the measuring syringe that comes with the product. Kitchen teaspoons vary significantly in volume and should never be used to measure medicine.

Home cooling measures that work

In addition to medication, several comfort measures can help your baby feel better:

Dress lightly: One breathable layer is enough. Bundling a feverish baby in blankets traps heat and can make the fever worse. Remove hats indoors.
Cool the room: Aim for a comfortable room temperature — approximately 68–72°F (20–22°C). A small fan circulating air (not blowing directly on the baby) can help.
Extra fluids: Fever increases fluid loss. Offer the breast or bottle more frequently than usual. Babies over 6 months can also be offered small sips of water or an oral rehydration solution if they are not feeding well.
Lukewarm sponge bath: A brief sponge bath with lukewarm (not cold) water can lower temperature temporarily and may soothe your baby. Sit them in a few centimetres of lukewarm water and gently sponge the neck, armpits, and groin where blood vessels are close to the skin.

Do not use alcohol rubs. Rubbing the skin with isopropyl or rubbing alcohol was a common practice decades ago but is now known to be dangerous. Alcohol is absorbed through an infant's skin and can cause toxicity, low blood sugar, and seizures.

Do not use ice packs or cold baths. Cold water causes blood vessels to constrict, which can actually raise core temperature. It also causes shivering, which generates more heat, and it distresses babies unnecessarily.

Common fever myths debunked

Several persistent misconceptions about infant fever lead parents to over-treat, under-treat, or panic unnecessarily.

Myth: "The fever itself is the disease and must be eliminated."
Fact: Fever is a symptom, not a diagnosis. A moderate fever (up to about 104°F / 40°C) is generally not harmful and may actually help the immune response. The goal of treatment is comfort, not a normal temperature on the thermometer.
Myth: "A febrile seizure will cause brain damage or lead to epilepsy."
Fact: Simple febrile seizures — the kind caused by fever in otherwise healthy children — do not damage the brain or significantly increase the risk of developing epilepsy. They are alarming to witness but are rarely medically serious. The main risk is injury if the child falls during the seizure.
Myth: "If the fever comes down with medication, it wasn't serious."
Fact: Even children with serious bacterial infections often respond temporarily to fever-reducing medication. The height of the fever and the response to medication cannot reliably rule out serious illness. Observe your baby's behaviour between doses — how they look and act when the fever is down matters more than the temperature itself.
Myth: "Teething causes a high fever."
Fact: Large studies have found that teething may slightly elevate gum temperature but does not cause a true systemic fever of 100.4°F (38°C) or above. If your teething baby has a fever, look for another explanation and follow the age-based guidelines above.
Myth: "You should give fever medicine immediately to prevent febrile seizures."
Fact: Clinical trials have shown that giving acetaminophen or ibuprofen at the first sign of fever does not prevent febrile seizures. Febrile seizures tend to occur at the onset of fever — often before parents even realise the child has one — and are not reliably prevented by medication.

Using Bebblo to track fever symptoms

When your baby is unwell, keeping a clear record of temperature readings, timing, medication doses, feeding, and sleep is invaluable — both for your own peace of mind and for the conversation with your pediatrician.

Bebblo lets you:

Log temperature readings with the time, method, and any notes — so you can see at a glance whether the fever is rising, stable, or coming down.
Record feeding sessions so you can quickly confirm your baby is still taking enough fluids, and flag changes in appetite to your doctor.
Track sleep to notice whether the fever is disrupting rest more than usual, which can itself be a useful clinical observation.

Having a timestamped log means you will not have to rely on memory when the doctor asks "When did the fever start?" or "How many doses of acetaminophen have you given?" Everything is in one place, stored locally on your phone.

Medical disclaimer: This article is for general informational purposes only and does not constitute medical advice. It does not replace the professional judgment of a licensed physician or paediatrician. Always consult your doctor or seek emergency care when in doubt about your baby's health. If you are concerned, call your doctor — even if you are unsure whether it is necessary.

Track your baby's health with Bebblo

Log temperature, feeding, and sleep with a single tap. Keep a clear record to share with your doctor — all stored locally on your phone, free, no mandatory account.