Fever in Children

Body temperature fluctuates throughout the day. It is at its lowest early in the morning, rises during the day and peaks between 4 p.m. and 6 p.m. Daily variations can be as much as 1°C, especially in active children or after physical activity.

Fever is an increase in the body's temperature beyond a certain threshold. A child has a fever when their rectal temperature, taken at rest, is 38.0°C or higher. Viral and bacterial infections, gastrointestinal problems and immunizations are the most common causes of fever in children. A high fever is not reflective of the severity of an illness. The child's behaviour is usually a better indication of how sick they are. A high fever may break out in a child who has a mild infection, while a child with a very serious infection may not have any fever at all.

Taking a child's temperature

There are several ways to take a child's temperature: the rectal method, oral method, axillary method (under the armpit), tympanic method (in the ear) and temporal artery method (forehead). For the most accurate measurement, it is important to choose an age-appropriate method and to use a proper technique. The following chart provides some guidance on the recommended method for taking a child's temperature based on age:

There are several types of thermometers on the market. Whichever one you choose, be sure to follow the manufacturer's instructions when it comes to using, cleaning and storing the thermometer. Digital thermometers (for rectal and oral use) are preferred because they are easy to use, easy to read and accurate. Do not use a mercury thermometer. If it breaks, you may be exposed to mercury, which is toxic and has an impact on human and environmental health. While it is quick to use, an infrared ear thermometer can give temperature readings that are too low, even when the manufacturer's directions are followed. Furthermore, it is not as accurate as a rectal thermometer. Devices that are passed over the front of the forehead use technology that is promising but are not yet recommended for accurate readings. And lastly, pacifier thermometers are less reliable than rectal thermometers.

Normal temperature ranges measured at different body sites vary. As a result, the measurements used to define a fever also differ. Below is a table that provides an overview of these measurements, as well as general comments on what is involved in taking the child's temperature.

When should I take my child to see doctor?

• Fever for more than 72 hours
• Has a skin rash, red blotches
• Has had a seizure
• Is lethargic, hard to wake up or unresponsive
• Is particularly cranky, fussy, or irritable
• Is crying and is inconsolable
• Is vomiting repeatedly
• Is persistently wheezing or coughing

Any child with a fever who is younger than 3 months of age should see a doctor or go to a hospital as quickly as possible. For children 3 to 6 months, we recommend calling your doctor or Info-Santé. They will tell you what to do.

What to do and what not to do

A child who is feverish should rest and drink plenty of fluids. They should wear light clothing and sleep with fewer blankets than normal so heat can leave the body and help lower their body temperature. Do not take off all the child's clothes as they could become too cold and start shivering, generating more body heat and causing their temperature to rise again. Alcohol rubs are not recommended because the product can be absorbed and be toxic for the child. Giving the child a lukewarm sponge bath is not recommended either.

Medication is not always needed to reduce a child's temperature. For example, a child who continues to play and eat normally despite having a fever does not require medication. When treatment is required, the first choice is acetaminophen (Tempra®, Tylenol®). Do not give acetaminophen to a child younger than 3 months without first talking to your doctor. Ask the pharmacist to show you which strength and form are best suited for your child, then calculate the appropriate dose based on your child's weight.

The second choice is ibuprofen (Motrin®, Advil®). The use of ibuprofen in children younger than 6 months is not recommended without first talking to your doctor, and should be avoided if the child is not drinking and eating reasonably well. Ask the pharmacist to advise you with regards to the product and exact dose to administer. Unless specifically advised by a health professional, children and teenagers with a fever should never take acetylsalicylic acid (Aspirin®). If the fever is caused by a viral infection, taking aspirin can increase the risk of Reye's syndrome, a very serious condition that can damage the liver and brain.

For more information:

Canadian Paediatric Society

www.cps.ca