Fevers Explained: How Medications Work in Lowering a Temperature

Mar 31, 2011
Elizabeth Batt

group-A Streptococci (right wedge) bacteria is responsible for Strep Throat - CDC/ Dr. Richard Facklam

Dr. Paul Langevin explains the processes surrounding a fever. What causes an elevation in temperature and how do antipyretic medications work?

The American Academy of Pediatrics (AAP) recently launched a fever phobia campaign by asking pediatricians to educate parents on all aspects of a fever. The message of the campaign was simple: parents should focus more on the illness causing the fever, rather than the fever itself.

All parents know when their child has a fever, but the actual process involved in temperature elevation is more elusive. Suite101 asked Dr. Paul Langevin, Director of Cardiac Anesthesia and Peri-operative Care at Hahnemann University Hospital in Philadelphia, to explain just how a fever develops.

Dr. Langevin lectures globally and is trained in Internal Medicine, Anesthesiology, Critical Care and Non Invasive Cardiology. Actively engaged in training young physicians, he has received numerous awards for his research and teaching and has been published in Anesthesia & Analgesia, and the journal, Anesthesiology.

How is the temperature regulated?

A thermostat located in an area of the brain called the hypothalamus regulates our body temperature. Just like the thermostat in our home, the hypothalamus can adjust our body temperature up or down and when it is set higher, a fever results. Now many things can adjust the thermostat in our home. The children may play with it. A workman may damage it. The man of the house may turn it down or a mom may feel it needs to be warmer for the new baby. Some of these may be helpful, others not. Similarly, there are many reasons why the thermostat in our bodies may be adjusted.

In most cases, the hypothalamus altars its setting when it is exposed to a substance in our blood called a pyrogen. [A fever producing substance or organism]. Yet fevers may result from many other causes including the over production of thyroid hormone, certain drugs or even simple ovulation. Hence fevers may occur for a variety of reasons only some of which are concerning. A fever may well occur for no apparent reason and in the absence of any obvious illness. In young healthy children however an infection, (viral or bacterial) probably remains the most common cause of fever. Infectious fevers tend to result from circulating pyrogens.

How are pyrogens produced?

Pyrogens may be produced by our bodies (endogenous) or they may come from something outside (exogenous). Exogenous pyrogens often stimulate the release of endogenous pyrogens, which then adjust the hypothalamus to a higher setting causing a fever. Exogenous pyrogens include compounds that come from bacteria and viruses such as lipopolysaccharide.

Some drugs can produce fever in small numbers of patients and would therefore qualify as exogenous pyrogens. Endogenous pyrogens include biochemicals secreted by our bodies (eg PGE2 and interleukin 6) and these are often secreted in response to exogenous pyogens although they can arise from other sources including certain cancers.

Are fevers beneficial?

Whether a fever is actually helpful in overcoming an infection or simply the result of pyrogens that reset the hypothalamus, remains controversial. Some authorities believe that elevations in body temperature inhibit some bacteria and viruses. Others believe that our bodies natural defenses operate better at elevated temperature. It may be that sometimes fever is helpful – while in other cases, it is not.

How dangerous are typical fevers and should we worry about them?

When fevers occur, they should heighten our index of suspicion of an illness. This is especially true in children or debilitated patients who may be unable to describe what doesn't feel right. Even with low grade temperatures, the cause of the fever may require attention even if the fever itself does not. For example, a fever of 102° F doesn't have to be treated but if that fever is caused by an ear infection or a strep throat, then an antibiotic is needed.

Yet most fevers are associated with benign viral illnesses that are self-limited. Our ability to treat them is poor and they really do have to run their course. Consequently, our therapy of viral illnesses is directed at preventing dehydration (i.e. fluids) and providing symptomatic relief. The associated fever needs to be watched treated appropriately.

What is appropriate therapy for a fever and should a child with a fever always be treated?

Fevers make people feel miserable with joint pain, body aches, somnolence and fatigue. So while a fever itself may not warrant medication, the symptoms associated with it often make them desirable. Making the patient, especially a child, more comfortable is paramount but parents should not be overly zealous in their attempts to control a low-grade fever.

Dressing the child in light, minimal clothing will allow them to dissipate heat. However we often feel cold when we raise a fever and for low-grade fevers, there is no reason not to wrap the child in a blanket if it makes them feel better.

What are antipyretics and how do they work?

Medications known to reduce fever by readjusting the set point of the hypothalamus are called antipyretics and include MOTRIN® and TYLENOL®. These agents can "break" a fever and make patients feel profoundly better. Tylenol and Motrin can be alternated and should never be used in more than recommended doses. Aspirin is also an antipyretic but it can cause a serious neurological injury in children, (Reye's syndrome), and should never be used in children except on the specific advice of a physician.

What about higher fevers, are they dangerous and do they need to be reduced?

Generally speaking, younger patients tolerate fevers better than older patients. Regardless of age however, very high fevers can be extremely serious causing seizure or even permanent brain injury. Yet fevers below 105 F in young children, and below 104° F in adults, rarely cause permanent sequellae. Higher fevers approaching worrisome temperatures should probably be reduced.

Uncovering the child or placing them in a tepid bath can reduce temperatures and may be especially effective along with the judicious use of antipyretics. Fevers associated with other symptoms, fevers that do not resolve and fevers approaching 103° F, should always prompt a call to the doctor. For lower temps, especially in the absence of other symptoms, a watchful eye for a developing illness and loving attention to make the child feel better is frequently all that is required. Always, a simple call to the pediatrician can be very reassuring.

Suite101 thanks Dr. Langevin for sharing his expertise and insight.

Final thoughts on fevers from pediatrician, Dr. Weissbluth

Dr. Daniel Weissbluth is a pediatrician at Northwestern Children’s Practice in Streeterville, Chicago. As an instructor of clinical pediatrics at the Northwestern University School of Medicine, his main area of interest concerns the effects of media on childhood. Weissbluth says that in general, with the exception of heat stroke, a fever "is a good sign that the child's body is fighting off infection," and "is the result of illness not the cause of the illness."

Furthermore adds Weissbluth, he does not consider a temperature of 99° F, a fever. The "commonly accepted "cut-off" for a fever," is 100.4° F," he says, but, "there are many other factors that get pediatricians concerned about fevers: age of child, other concurrent symptoms, duration of fever. It is an unlikely scenario where a child has an isolated fever without any other symptoms," says Weissbluth. It's also important to also remember that, "body temperature normally rises in the late afternoon and evening or after strenuous exercise," he adds.

Weissbluth, who lives in Chicago, contributes to the website, The Weissbluth Method, and is the creator of the Weissbluth Method Toddler Bedtime App for the iPhone, an app designed to help parents determine when to put their children down to sleep.

So why do parents fear a fever? America's Top Pediatrician (2004-05), Dr. Arthur Lavin, answers this question and more in Suite101.com's, "American Academy of Pediatrics Launches Fever Phobia Campaign." Meanwhile, one of the most disconcerting aspects of a fever for parents involves febrile seizures and whether they are dangerous. Dr. Anatoly Belilovsky discusses the different types of fever-related seizures and which types, parents should concern themselves with in, "Fever Phobia: Sometimes the Lack of a Fever Has a Worse Outcome."

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