A fever is one of the most tell tale signs that we may be experiencing an infectious illness. While they may be associated with undesirable symptoms, fevers are not all bad. Let’s discuss what a fever is, what to expect with a fever, and how to manage these symptoms.

What is a fever?

A fever is defined as a body temperature greater than or equal to 100.4 Fahrenheit or 38 degrees Celsius. This number does not change based on age, gender or what a person’s “baseline” body temperature may be. The most accurate way to measure body temperature is to obtain a “core” temperature – in older children and adults this is done by checking the temperature under the arm (axillary) or under the tongue (oral). In infants the best way to measure the core body temperature is by using a rectal thermometer.

A fever is a normal part of our immune system’s response to an infection. Especially with viruses, fevers tend to be one of the first signs of illness and sometimes can occur before any other symptoms have appeared. Your body temperature may then fluctuate over the next hours to days while your immune system responds to the threat.

What to expect when a fever spikes

When our body temperature spikes, we may experience some other uncomfortable symptoms such as fatigue, headache or body aches, poor appetite, nausea, chills or even intense shaking called “rigors”. These symptoms combined with the increased evaporative losses we experience from sweating are the main reasons we typically treat fevers.

The goal when using medications to treat fevers should focus on achieving comfort rather than reaching a specific number. Medications such as acetaminophen (Tylenol) or ibuprofen (Advil, Motrin) will help to lower your body temperature and allow you to be more comfortable so that you can rest and replete these fluid losses.

Which medication should you choose?

Tylenol is safe to use at any age, but should be given only with the guidance of a pediatrician in a child under 2 months of age. Tylenol is metabolized in the liver and lasts for 4 hours. Ibuprofen works via the kidneys, is safe to use in anyone 6 months of age or older, lasts a little longer (6 hours) and includes an anti-inflammatory component that acetaminophen lacks. Because of their mechanism of action, Ibuprofen and other NSAIDs such as Naproxen are specifically helpful at alleviating pain from menstrual cramps in addition to fever and body aches. Aspirin should be avoided in children under the age of 19 unless specifically prescribed by a pediatrician to avoid a rare of potentially serious complication called Reye Syndrome.

In addition to using medications to lower your temperature, allowing your body to rest and drinking plenty of fluids can also help fight off illnesses faster.

When should you be concerned?

A fever may be a normal part of our immune system’s response to illness, but some situations may warrant further investigation by a doctor. If you are experiencing fevers for more than 4 days, fevers that do not respond to medication or severe symptoms such as lethargy, dehydration or seizures – talk to your doctor.