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PEDIATRICS

Fever in an Infant

It can be very worrisome when your baby is sick. If your baby is 3 months old or less and has a fever, they should be seen by a doctor urgently.

What is a Normal Body Temperature?

The normal average body temperature is 37°C (98.6°F) when measured orally. Body temperature can fluctuate quite a bit through the day depending on what your baby is doing, what they are wearing, and what kind of climate conditions they are exposed to.

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Your baby's temperature can be taken in different ways: taken under the tongue (orally), in the ear (tympanic), under the arm (axillary) and rectally. All of these methods can vary by a few decimals: 

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Rectum

36.6°C to 37.9°C (97.9°F to 100.2°F) 

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Mouth

35.5°C to 37.5°C (95.9°F to 99.5°F) 

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Armpit

36.5°C to 37.5°C (97.8°F to 99.5°F) 

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Ear

35.8°C to 37.9°C (96.4°F to 100.2°F) 

What is a Fever?

A fever is body temperature that is higher than average. It is a normal response to infection and other illnesses. Fever helps the body fight infection and can be a symptom of illness or disease, either minor or serious. Fever itself is not a disease but a sign that the body is fighting something.

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Ear or rectal temperature:

  • Fever: 38°C (100.4°F) to 39.9°C (103.9°F) 

  • High fever: 40°C (104°F) and higher

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Oral or armpit temperature:

  • Fever: 37.6°C (99.7°F) to 39.4°C (102.9°F) 

  • High fever: 39.8°C (103.6°F) and higher

What Causes a Fever?

Viral infections, like those that cause colds and flu, are one of the most common causes of fever. Fevers can also be caused by bacterial infections like a urinary tract infection (bladder infection), pneumonia or an ear infection. In a young infant (0-3 months), fever can be a sign of serious bacterial illness, like meningitis, and they should be seen by a doctor urgently. 

 

Fevers can also be caused by other processes inside the body such as inflammation, allergic reaction, cancer or autoimmune disorders. Your baby can also get a fever from being too hot, like when sitting outside in the sun for too long or being in a car on a hot day. 

Treating a Fever

Fever is a symptom of something else going on in the body. Most fevers will go away once the illness causing it clears up. See our section on Cold and Flu for tips on how to treat these conditions, if this is what is causing your baby's fever. You can treat your baby's fever with over the counter medication like Tylenol or Advil. If you are unsure about how to dose over-the-counter medications for your baby, speak to your pharmacist, doctor or nurse for guidance. 

 

If your baby's fever is from a bacterial infection, you may need to see a doctor or pharmacist for treatment. 

 

Try to dress your baby in light clothing when they have a fever, and keep the room temperature at 21°C (70°F) or lower to help them keep cool. 

See a Doctor if Any of the Following Occur

  • Your baby is dehydrated and unable to keep water down. Signs that your baby may be dehydrated include not producing as many wet diapers as usual and not drinking as much as they usually do. 

  • Rash that accompanies their fever 

  • Signs of a bacterial infections like: tugging at their ears, crying more than usual, not being able to soothe your baby (irritability) 

  • Your baby is persistently wheezing or coughing 

  • The fever lasts more than 48-72 hours 

  • Excessive sleepiness, lethargy or your baby does not respond 

  • If your baby is under 3 months or you are concerned for their wellbeing, you should see a doctor

Preventing Fevers

Fevers are a normal reaction to infection. The only way to prevent them is to prevent infection. Wash your hands frequently and wear a mask when out in large groups during cold and flu season.

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Having up to date immunizations can also protect your baby from illnesses.

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