It’s gettin’ hot in here…
Recognizing fever’s role in fighting illness
Childhood fevers rank near the top of the list for reasons to call the doctor this time of year. Perhaps the most misunderstood immune response, fever is a major concern for most parents. It is important to remember, however, that fever plays an important role in the body’s natural immune response to infections, and most of the time, should be left alone to do its job.
Fevers are caused by a series of reactions within the body. First, proteins released by the infectious virus or bacteria, or perhaps proteins liberated from the destruction of our own cells, trigger the set-point of the body’s thermostat, located at the base of the brain, to increase. This is just like when you get home and turn the thermostat up in your home. The dial says one thing, but the house is still cold. So, the body works to raise its internal temperature through heat-promoting mechanisms, such as vasoconstriction and shivering. After several hours, the body temperature reaches the new set-point, or level on the thermostat, and the chills disappear. The body will maintain this temperature until the stress (read, infection) that caused the temperature to rise is removed.
The next stage of a fever is the “flush.” After the immune system has worked to eliminate the initial stressor, the body’s thermostat is returned to normal. Since the individual’s body temperature is still high, the body uses its internal heat-losing mechanisms to normalize itself. These include sweating and vasodilation, which pumps blood out to the surface of the body. This is what we mean when we say “the fever broke.” Both the flush and the switch to sweating are signs that the body temperature is decreasing.
Though they may be uncomfortable, fevers are an important part of the body’s immune response. The chemical messengers our bodies use to turn the thermostat up increase the production of antibodies and important immune cells called T-cells. The higher temperature also increases the ability of white blood cells to digest infectious agents. Fever increases heart rate, speeding the delivery of important immune cells to sites of infection. In addition, the higher temperature speeds up all the biochemical reactions in our body, which is thought to help our bodies repair cells damaged by infection more quickly.
Scientific research confirms the benefits of fever. A series of classical fever experiments has shown that when fever is suppressed, there is substantially more mortality. In contrast, an increase in body temperature within the range seen in natural fever has been shown to increase resistance to infection. Human studies have demonstrated that kids with chickenpox that are given acetaminophen (brand name
Tylenol) take longer to achieve total crusting of their lesions, as compared to sick kids given a sugar pill. This means that they are contagious for a longer period of time. Likewise, when adults infected with the common cold virus take aspirin to reduce their fever, they are also more contagious, as measured by viral shedding. Additionally, therapy to bring down fevers in patients with the common cold is associated with a decreased antibody response and an increase in cold symptoms. In contrast, there is no evidence that shows that the increases in body temperature encountered during a natural fever are harmful.