Dr. Hanna Saadah - Fever is the elevation of the body temperature above normal. Under ordinary situations the body produces more heat than is required to maintain normal temperatures. However, normal body temperatures are strictly maintained in spite of environmental variations by balancing the heat generated from our metabolism, livers, and muscles against the heat dissipated from our skin and lungs.

The body’s temperature is regulated by our brain’s thermostat, the hypothalamus. When the hypothalamus is reset upward, it triggers the body’s mechanisms that generate and conserve heat such as constriction of skin blood vessels and muscle shivering; when it is reset downward, it triggers mechanisms that dissipate heat such as the opening of the skin blood vessels (flushing), sweating, and rapid breathing.

The average oral temperature is about 36.8 degrees Centigrade or 98.2 degrees Fahrenheit and tends to be lowest at 6 a.m. and highest at 4 p.m. The maximum normal oral temperature is 37.2 °C or 98.9 °F at 6 a.m. and 37.7 °C or 99.9 °F at 4 p.m. Rectal temperatures are about 0.4 °C or 0.7 °F above oral readings. Consequently, temperatures higher than these normal temperatures are considered fevers.

Fever is our body’s reaction to injury, inflammation, certain hormonal storms, and infections—all of which release certain chemicals called toxins and cytokines, which reset the hypothalamus thermostat upwards. When that happens, the skin blood vessels constrict to conserve heat—the muscles shiver and the liver increases it metabolism to generate heat. This process continues until the temperature reaches the higher-set level. The reverse happens when the hypothalamus resets the temperature down, causing the skin to flush and sweat and the lungs to breath faster, thus cooling off the body.

Fever does not help the body’s fight against infection and reducing it does not hinder the body’s defenses. Therefore, fever needs to be treated only if it renders the patient uncomfortable. Otherwise, fever should only be monitored because it gives very valuable information about the progress of disease. Very high fevers, however, may cause seizures, especially in children, and should be promptly treated with medicines and by cooling the body in a water bath.

The treatment of fever rests on the use of antipyretics (Tylenol, Aspirin, and others) all of which reset the hypothalamus thermostat down. Conversely, medications that suppress sweating (anti-cholinergics) or flushing (vasoconstrictors) may interfere with the body’s cooling mechanisms and increase fever.

There are fevers that do not obey the settings of the body’s thermostat. These conditions may occur when heat generation is excessive and heat dissipation is limited by hot external conditions. Examples include laboring or exercising in very hot weather. In such situations the heat generated exceeds the heat dissipated, causing a condition known as hyperthermia, which may lead to heat strokes. Here, using Aspirin or Tylenol will do no good because the body’s thermostat is already set low and lowering it further does not help. Moving to a cooler place and bathing in cool water are the quickest means that reduce this kind of high fever.

Many conditions that directly affect the brain such as hemorrhages and strokes can reset the brain’s thermostat upward, causing high fever. In such cases, it may prove more difficult to reset the thermostat down with medications alone. Moreover, certain medicines can cause very high fevers by directly resetting the brain’s thermostat upward. For example: a) antipsychotics, which block the brain’s hormone dopamine, may cause a very dangerous condition known as the Neuroleptic Malignant Syndrome; b) general anesthetics, in the genetically inclined, may cause an equally dangerous condition called Malignant Hyperthermia; and c) certain antidepressants may cause the deadly Serotonin Syndrome. The treatments for these serious conditions are very complex and require high expertise.

Antibiotics, which are used to treat infections, can themselves cause a high fever known as Antibiotic Fever. The only treatment for this condition is to stop the antibiotics, which causes the fever to defervesce within a few days. Other conditions such as old age, kidney failure, septicemia, and certain medications such as steroids prevent the brain’s thermostat from resetting upward, thus masking fevers and making infections much harder to diagnose.

Although infections do cause fever, not all infections cause fever and not all infections require antibiotics. Viral illnesses such as colds, sore throats, bronchitis etc. will not respond to antibiotics, which can only cause adverse effects. On the other hand, febrile bacterial infections such as pneumonia, strep throat, kidney infections, etc. need prompt antibiotic therapy. Fever is just a warning sign, indicating that something is wrong; finding the cause and deciding whether to treat or not to treat are the real issues.