What Causes a Fever, or Elevated Body Temperature?

Normal body temperature is 37 degrees Celsius or 98.6 degrees Fahrenheit. This is the core optimal temperature of the human body. But sometimes, when a person becomes sick with a bacterial or viral infection, a fever develops. Fever is when the core body temperature exceeds the norm, and the body's immune system increases this temperature to help fight invading pathogens.

What Triggers a Fever?
Fever results when chemicals called pyrogens trigger the brain's hypothalamus to increase body temperature. There are a number of chemicals that can act as pyrogens, including:

• Bacterial toxins
• Cytoplasmic contents of bacteria that have been destroyed
• Antibody-antigen complexes
• Interleukin-I (IL-1)

The presence of pyrogens are indicative of infection, and increasing the body temperature confers a number of benefits in the battle against an illness. Pyrogens can:

• Enhance the effects of interferons (chemicals involved in immune response)
• Inhibit growth of some microorganisms
• Enhance the performance of white blood cells of the immune system
• Enhance the process of tissue repair

So a low or moderate fever is useful to the body, and helps in the fight against pathogenic microbes. This is because many microbes that infect humans thrive at normal body temperature, so when the body turns up the heat, it is trying to create an environment in which these microbes are less able to thrive.

Taking medications to reduce a low fever can actually interfere with the body's healing process. However, when a fever exceeds a certain temperature it can become dangerous.

When Is a Fever Too High?

A high fever resulting from an infection rarely becomes dangerous. It's not unusual for someone who is ill to run a temperature of 104 or even 105 degrees F. However, fevers that are due to infection rarely exceed 106 degrees F. To disable the body's proteins and to cause damage the brain, a fever typically must reach or exceed 107 or 108 degrees F, something that is more likely in cases of heat stroke than infection. Maintaining hydration is extremely important when running a fever, since fluid requirements go up approximately 10% for every degree of fever. So, when fever present, drinking plenty of fluids is essential.

Although fever is a natural response of the body to infection, it is best to err on the side of caution. Always consult your health care practitioner if you or your child becomes ill. Medical professional have the training to make sound judgments as to when and which measures should be taken to reduce a fever and when a fever should be left alone.

Sources

Bauman, R. (2003) Microbiology. Peasrson Benjamin Cummings.
Tortora, G; Funke, B; Case, C. (2010) Microbiology: An Introduction. Benjamin Cummings.

Please note: The information in this article is not to be followed as medical advice, diagnosis or treatment. Please consult with your physician or primary health practitioner for information regarding your own personal health and necessary treatments.