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What You Need to Know About Fever and Taking Your Child’s Temperature

Sep 21, 2021
child getting their temperature taken.

Fever is a common symptom of illness. But why do fevers occur, what is the best way to take a temperature and what should you do if the reading is high?

What Is a Fever and Why Does It Occur?

Fever is an elevation of the body’s internal temperature. Our temperature is regulated in a part of the brain called the hypothalamus. Think of it like a thermostat. If our temperature goes too high, the brain tells our body to sweat, and we are motivated to seek cooler conditions. Likewise, if our temperature goes too low, the brain tells muscles to shiver (which generates heat) and we are motivated to pull up the covers or put on a coat.

A fever occurs when the “set point” of our body’s thermostat increases to a higher level. We feel cold, even though our body temperature is really normal. We shiver and throw on a blanket and a fever is born. When the “set point” returns to normal, we sweat and take off the covers as the brain instructs our body to return to a normal temperature.

The most common cause of an elevated “set point” and fever is our immune system responding to an infection. However, there are other possibilities, including autoimmune diseases and brain injury.

Is the Number Important?

Traditionally, normal body temperature in humans was described as 98.6 F (37 C). The truth is that there is a wide range of normal body temperatures between 97 and 100 F. By definition, a fever is body temperature of 100.4 F (38 C) or higher.

This number is important because medical decisions are often made based on the presence or absence of a true fever and how many days a true fever has been present.

Is Feeling the Skin a Useful Way to Identify a Fever?

Feeling the warmth of your child’s skin is a good screening tool to discover if a fever might be present. However, some children feel warm despite having a normal body temperature. If you think a fever is present, it is best to take your child’s temperature to verify the fever and make note of the number.

What Kind of Thermometer Should I Use?

Digital thermometers are best because they are reliable and easy to read. Be sure to follow the instructions that accompany your thermometer to get the most accurate reading. Glass thermometers and thermometers containing mercury should be avoided and discarded as hazardous waste. Your local health department can assist with proper disposal and can help you find a safe alternative.

Should I Add or Subtract a Degree?

Rectal temperatures are the gold standard for evaluating internal body temperature. Temperatures taken at other locations, including the skin, mouth, armpit and ear may be more or less than the rectal temperature. Interpreting the significance of a temperature taken at a particular location is best left to your medical provider. Simply let your provider know where you took the temperature and the exact number you recorded.

What Should I Do if My Child Has a Fever?

If your child is less than 6 months of age, let your doctor know right away about any fever that develops. Children of any age with a fever lasting more than a couple days should also be seen. Fever-reducers, such as acetaminophen and ibuprofen, work to bring the body temperature back to normal and will help your child feel better. Acetaminophen (Tylenol®) may be used in all children over 2 months. Ibuprofen (Advil®, Motrin®) may be used in children over 6 months. Be sure to follow the instructions on the label, paying close attention to the proper dose for your child’s age and weight. It is also important to drink plenty of fluids when fever occurs. Be sure to follow the instructions on the label, paying close attention to the proper dose for your child’s age and weight. It is also important to drink plenty of fluids when fever occurs.

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Nationwide Children's Hospital Medical Professional
Mike Patrick, MD
Emergency Medicine; Host of PediaCast

Dr. Mike Patrick is an Assistant Professor of Pediatrics at the Ohio State University College of Medicine and Medical Director of Interactive Media for Nationwide Children's Hospital. Since 2006, he has hosted the award-winning PediaCast, a pediatric podcast for parents. Dr. Mike also produces a national podcast for healthcare providers—PediaCast CME, which explores general pediatric and faculty development topics and offers free AMA PRA Category 1 Credit™ to listeners.

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700 Children’s® features the most current pediatric health care information and research from our pediatric experts – physicians and specialists who have seen it all. Many of them are parents and bring a special understanding to what our patients and families experience. If you have a child – or care for a child – 700 Children’s was created especially for you.