Fever refers to an elevation in body temperature. Technically, any body temperature above the normal oral measurement of 98.6 F (37 C) or the normal rectal temperature of 99 F (37.2 C) is considered to be elevated. However, these are averages, and one's normal body temperature may actually be 1 F (0.6 C) or more above or below the average of 98.6 F. Body temperature can also vary up to 1 F (0.6 C) throughout the day.


Fever is not considered medically significant until body temperature is above 100.4 F (38 C). Anything above normal but below 100.4 F (38 C) is considered a low-grade fever. Fever serves as one of the body's natural defenses against bacteria and viruses which cannot live at a higher temperature. For that reason, low fevers should normally go untreated, unless accompanied by troubling symptoms.
Also, the body's defense mechanisms seem to work more efficiently at a higher temperature. Fever is just one part of an illness, many times no more important than the presence of other symptoms such as cough, sore throat,fatigue, joint pains or aches, chills, nausea, etc.
Fevers of 104 F (40 C) or higher demand immediate home treatment and subsequent medical attention, as they can result in delirium andconvulsions, particularly in infants and children.
Fever should not be confused with hyperthermia, which is a defect in your body's response to heat (thermoregulation), which can also raise the body temperature. This is usually caused by external sources such as being in a hot environment.


A fever is usually accompanied by sickness behavior, which consists of lethargy, depression, anorexia, sleepiness, hyperalgesia, and the inability to concentrate. Symptoms can include a runny nose, sore throat, cough, hoarseness, and muscle aches. Viruses also may cause diarrhea, vomiting, or an upset stomach.


For the most part, these viral illnesses will improve simply with time. Antibiotics will not treat a virus. Symptoms can be treated using decongestants and cough medicine bought over the counter. If diarrhea or vomiting occurs, then the person needs to be encouraged to drink fluids.


Gatorade or sports drinks will replace lost electrolytes. If fluids are not staying down, then the doctor should be notified. Viral illnesses can last as long as one to two weeks.


The influenza virus is a major cause of death and serious illness in the elderly. Symptoms include headaches and muscle and joint aches, as well as the other common viral symptoms, including fever. Vaccines against seasonal influenza as well as H1N1 influenza are available.


Also, antiviral medications can be administered to fight the influenza virus immediately after the symptoms start. This illness usually occurs during the winter.


Bacterial fever


Bacterial illnesses causing fever can affect almost any organ system in the body. They can be treated with antibiotics.


Central nervous system (brain and spinal cord) infections can cause fever, headache, neck stiffness, or confusion. A person may feel lethargic and irritable, and light may irritate the eyes. This could represent meningitis or abrain infection, so the person should go immediately to the doctor.


Lower respiratory system infections include pneumonia and bronchitis can cause fever. Symptoms include coughing, difficulty breathing, thick mucus production, and sometimes chest pain.


Upper respiratory system infections occur in the throat, ears, nose, and sinuses. A runny nose, headache, cough, or sore throat accompanied by a fever may indicate a bacterial infection, but a viral infection is the most common cause.


Infection of the genitourinary system may cause a person to have a burning sensation when urinating, blood in the urine, the urge to urinate frequently, andback pain along with a fever. This would indicate an infection in the bladder, kidney, or urinary tract. Antibiotics would treat such an infection.


If the reproductive system is affected, people often see a discharge from the penis or vagina and have pelvic pain along with the fever. This may representpelvic inflammatory disease (PID), which can cause significant damage to the reproductive organs. In this case, the person and any sexual partners should see a physician.


Gastrointestinal system (digestive system) infections are indicated by diarrhea, vomiting, stomach upset, and sometimes blood in the stool. Blood in the stool can indicate a bacterial infection or other serious illness. Abdominal pain may be caused by an infection of the appendix, gallbladder, or liver, and medical care should be accessed.


The circulatory system (including the heart and lungs) can be invaded by bacteria. There may not be any specific symptoms with the fever. A person may feel body aches, chills, weakness, or confusion. The condition of sepsisexists when bacteria enter the bloodstream. An infection of a heart valve can occur in people who had heart surgery in the past and in people who use IV drugs. This condition requires hospitalization and immediate treatment with IV antibiotics.


Skin, the largest organ in our body, can also be the source of a bacterial infection. Redness, swelling, warmth, pus, or pain occurs at the site of the infection. An infection may result from trauma to the skin or even a clogged pore that becomes an abscess. Sometimes the infection needs to be drained. Antibiotics are often needed. In addition, skin can react to some toxins by producing a rash; for example, the scarlatina rash that can occur after a Strep throat infection causes scarlet fever (rash is bright red and diffuse, with some skin that develops scaling and desquamation or skin peeling off).


Fungal fever


Fungal infections can affect any organ system. Often a physician can identify these infections through a physical examination. Sometimes further testing is required and in rare instances, fungal fevers may require a biopsy to diagnose the infection. An antifungal medication will usually treat the infection.


Animal exposure fever


Certain people who work with animals can be exposed to rare bacteria that can cause fevers. In addition to the fever, the person may have chills, headache, and muscle and joint aches. These bacteria can exist in livestock, in unpasteurized dairy products, and in the urine of infected animals.


Travelers' fever


Anyone who travels, especially outside the United States, may develop fever after exposure to various new foods, toxins, insects, or vaccine-preventable diseases.


The only vaccines required by law at this time are yellow fever and cholera.Childhood vaccines such as those against measles, mumps, rubella, diphtheria,tetanus, and polio should be current prior to travel. Vaccines against hepatitis A, meningitis, and typhoid can be obtained before people travel to an area where exposure to those diseases is likely. The U.S. Centers for Disease Control and Prevention (CDC) can advise you on the current vaccines recommended for travel to various countries.


When traveling, consumption of contaminated water, uncooked vegetables, or unpasteurized dairy products can cause a low-grade fever and traveler's diarrhea.Bismuth subsalicylate (Pepto-Bismol), loperamide (Imodium), and certain antibiotics can help reduce symptoms but in some people, may prolong the disease.


The symptoms of abdominal cramping, nausea, vomiting, headache, and bloating should go away in three to six days. A fever higher than 101 F (38.3 C) or the presence of blood in the stool is an indication to go to a doctor immediately.


Insect bites are a common way that infections are spread in some countries. Malaria is a serious infection that can occur after a mosquito bite. The bitten person may have fevers that come and go every few days. A blood test must be done to make the diagnosis. In certain infected areas, a traveler can take medication to prevent malaria. Lyme disease is spread by the bite of a tick. This is common in areas of the U.S. where the deer tick is found. Any infection caused by an insect bite should be evaluated by a doctor.


Drug fever


A fever that occurs after starting a new medication, without another source, may be a drug fever. The fever can occur at any time after starting the drug and should go away after the drug is stopped. Some drugs that have been associated with fever include beta-lactam antibiotics, procainamide (Procanbid), isoniazid, alpha-methyldopa, quinidine (Quinaglute Dura-Tabs), and diphenylhydantoin.


An immediate fever may be caused by an allergic response to the medication or a preservative in the medication.


Blood clot fever


Occasionally a blood clot can develop in a person's leg and cause swelling and pain in the calf. Part of this clot may break off and travel to the lungs. This may cause chest pain and trouble breathing. In either case, a person may develop a fever because of inflammation in the blood vessels. A person with any of these symptoms should go to the hospital.


Tumor fever


Cancer can cause fever in a variety of ways. Sometimes the tumor makes pyrogens, chemicals which cause a fever on their own. Some tumors may become infected. Tumors in the brain may prevent the hypothalamus (the body's thermostat) from regulating the body temperature. Many of the medications that a cancer patient takes can cause a fever. Finally, immune systems in cancer patients may be weakened, which makes them prone to various infections.


Environmental fever


Occasionally a very high body temperature can be reached when the body becomes overheated. This condition is called hyperthermia. This often occurs with strenuous exercise or when the body is exposed to hot or humid weather. Certain drugs that alter a person's behavior may prevent that person from taking shelter from the heat.


People with hyperthermia may be confused, lethargic, or even comatose. They may have an extremely high temperature and may not be able to sweat. Hyperthermia is treated differently than other causes of fever; it is a medical emergency. The affected person must be cooled immediately.


Special medical conditions


Many people have medical illnesses that prevent their immune system (defense system) from working normally. This may make it easier for a fever-causing infection to invade their body. Depending on the illness, it may be difficult to find the source of the fever. A fever in a person with limited ability to fight off infection can be very dangerous. The collagen vascular diseases and autoimmune diseases (for example, systemic lupus erythematosus, rheumatoid arthritis, and polyarteritis nodosa) may be associated with fever.


Generally, if the fever does not cause discomfort, the fever itself need not be treated. It is not necessary to awaken an adult or child to treat a fever unless instructed to do so by your health-care practitioner.


The following fever-reducing medications may be used at home:


  • Acetaminophen (Tylenol and others) can be used to lower a fever. The recommended pediatric dose can be suggested by the child's health-care provider. Adults without liver disease or other health problems can take 1,000 mg (two "extra strength" tablets) every four to six hours or as directed by your physician.
  • Ibuprofen (Motrin/Advil) can also be used to break a fever in patients over 6 months of age. Discuss the best dose with your doctor. For adults, 400-600 mg (two to three 200 mg tablets) can be used every six hours.


Aspirin should not be used for fever in children or adolescents. Aspirin use in children and adolescents during a viral illness (especiallychickenpox and influenza, or flu) has been associated with Reye syndrome. Reye syndrome is a dangerous illness which causes prolonged vomiting, confusion, and even coma and liver failure.


An individual with a fever should be kept comfortable and not overdressed. Overdressing can cause the temperature to rise further. Tepid water (85 F [30 C]) baths are a home remedy that may help bring down a fever. Never immerse someone in ice water. This is a common misconception. Never sponge a child or an adult with alcohol; the alcohol fumes may be inhaled, causing many problems.

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