Fever in Children: How to Take Their Temperature

Fever is defined as an increase in body temperature above the normal range that is triggered by a signal from the brain, most frequently in response to an infection.

Fever is an excellent defence mechanism the human body uses to fight viruses and bacteria. An increase in body temperature helps activate certain immune and inflammatory responses, which in turn, help fight infection.

Causes of Fever in Children

Fever is not a disease. Rather, it is often a symptom of a viral or bacterial infection. And since young children are more susceptible to certain infections, they are more likely to experience fever, for example, when they have a cold or the flu, an ear infection, strep throat, or a tummy bug.

How Do I Know if My Child Has a Fever?

Fever can manifest in different ways in children. For example, your child may…

• be shivery
• have hot skin • have a higher heart rate than usual
• breathe faster than usual
• complain about being cold
• complain of a headache
• be less active than usual

To confirm whether or not your child has a fever, you will need to take their temperature.

How Do I Know if My Child Has a Fever?

Body temperature is measured with one of two types of thermometers: a digital thermometer with a special tip that is inserted in either the mouth, rectum, or armpit, or an ear thermometer, also known as a tympanic thermometer. Since ear thermometers are less accurate, they are not recommended for children under the age of two.

Never use a mercury thermometer, as it can break, exposing your child to the toxic substance.

The most accurate way to take your child’s temperature is to insert the tip of the thermometer into their rectum (rectal temperature). This method is recommended for babies and children under the age of five. For older children, temperature can be taken orally once they are able to hold the tip of the thermometer beneath their tongue while keeping their mouth closed (usually around the age of five). Axillary temperature (taken in the armpit) is also an option for babies and children.

It is important to read the manufacturer’s instructions before using the thermometer. Also, before taking your child’s temperature, be sure to wash your hands and clean the tip of the thermometer with warm water and soap.

If you are taking your child’s rectal temperature, dab a small amount of petroleum jelly on the thermometer tip before inserting it into their rectum.

If you are taking your child’s axillary temperature, place the tip of the thermometer in the centre of the armpit, then tuck the child’s arm snug against their body, to hold it in place.

Regardless of the technique, wait for the signal before removing the thermometer and checking the reading. For digital thermometers, it is important to thoroughly clean the thermometer with soapy water and rinse it well after each use.

A baby or child whose temperature reading is equal to or greater than the following temperature is considered to have a fever:

• 38.0°C, when measured rectally in babies under the age of 3 months
• 38.5°C, when measured rectally in children 3 months and older
• 37.5°C, when measured in the armpit
• 38.0°C, when measured beneath the tongue
• 38.0°C, when measured with an ear thermometer (last resort, since it is less accurate)

Should I Always Try to Bring Down a Fever?

If your child is still active despite the fever, and they continue to eat and drink, start by taking the following steps to make them more comfortable and reduce their body temperature:

• Give them fluids regularly, to avoid dehydration
• Keep room temperature around 21°C
• Dress them in light clothes and change them if they become damp
• Cover them with a light blanket when they are sleeping
• Keep them in a calm environment so they can rest
• Don’t force them to eat if they are not hungry Do not bathe your child in lukewarm or cold water.

Do not rub their skin with alcohol or place a fan nearby. This will only make them more uncomfortable and shivery.

Unless a health professional has given you a specific recommendation for your child, if the fever is causing them discomfort, or if the infection is also causing pain, it is possible to give them acetaminophen. Be sure to choose a formula that is appropriate for their age, e.g., concentrated drops, oral suspension, or chewable tablets, and determine the dosage based on their weight. In children 6 months and older, ibuprofen can also be used. These medications must be used in accordance with the directions, contraindications, and dosage recommended by the manufacturer. For liquid formulas, use the dropper provided with the product, to measure the dose accurately.

Never give aspirin to a child under the age of 18, except for certain specific medical conditions.

If your child’s fever persists, ask a health professional for advice, for example, by calling 811 or talking to your pharmacist.

When Should I Consult a Health Professional?

Babies under the age of 3 months should be taken to an emergency ward or a walk-in clinic if their rectal temperature is 38°C or higher, regardless of whether or not they are showing other symptoms.

In children 3 months or older, consider the child’s general state as well as the fever. Regardless of the fever they are running, if your child’s overall state is good, and they are able to eat and drink a bit, and are otherwise healthy, it is reasonable to wait before consulting a health practitioner. However, if your child suffers from a chronic disease, it is best to follow the instructions of their care team.

If the fever is accompanied by one or more of the following symptoms, consult a health professional without delay:

• Repeated vomiting (more than 6 or 7 times a day)
• Signs of dehydration (e.g., sunken eyes with dark circles under them; darker, less frequent urine; no tears when crying, excessive thirst, sunken fontanelles [soft spots on the head])
• Sleepiness or lethargy
• Persistent irritability or inconsolable crying
• Skin rash • Severe headache or neck pain or stiffness
• Confusion
• Difficulty swallowing
• Convulsions

It is also recommended you take your child to see a health professional if the fever persists longer than 2 or 3 days.

In short, don’t rely solely on the thermometer reading. A low fever in a very lethargic child who refuses to eat is more cause for concern than a higher fever in a child who continues to be active and to eat and drink.

When in doubt, don’t hesitate to ask a health professional for advice, for example by calling Info-Santé (811) or talking to your family pharmacist.