Why fever happens?

Question

Why is it human has fever?

Answer 1

Normal body temperature varies by person, age, activity, and time of day. The average normal body temperature is 98.6°F (37°C).

Considerations Return to top

Normal body temperature is a moving target:

In children younger than six months of age, the daily variation is small.
In children 6 months to 2 years old, the daily variation is about 1 degree.
Daily variations gradually increase to 2 degrees per day by age six.
Body temperature varies less in adults. However, a woman's menstrual cycle can elevate temperature by one degree or more.

Your body temperature is usually highest in the evening. It can be raised by physical activity, strong emotion, eating, heavy clothing, medications, high room temperature, and high humidity. This is especially true in children.

A rectal temperature up to 100.4°F (38°C) may be entirely normal. A rectal temperature of 100.5°F or above should always be considered a fever. Lower values might be a fever, depending on the person.

Fever is not an illness. Far from being an enemy, it is an important part of the body's defense against infection. Many infants and children develop high fevers with minor viral illnesses. While a fever signals to us that a battle might be going on in the body, the fever is fighting for the person, not against.

Most bacteria and viruses that cause infections in people thrive best at 98.6°F. Raising the temperature a few degrees can give your body the winning edge. In addition, a fever activates the body's immune system to make more white blood cells, antibodies, and other infection-fighting agents.

Many parents fear that fevers will cause brain damage. Brain damage from a fever generally will not occur unless the fever is over 107.6°F (42°C). Many parents also fear that untreated fevers will keep going higher and higher. Untreated fevers caused by infection will seldom go over 105°F unless the child is overdressed, or trapped in a hot place. The brain's thermostat will stop the fever from climbing above 106°F.

Some parents fear that fevers will cause seizures. For the great majority of children, this is not the case. However, febrile seizures do occur in some children. Once a child is already known to have a high fever, a febrile seizure is unlikely with the current illness. In any event, simple febrile seizures are over in moments with no lasting consequences.

Although infections are the most common causes of elevated body temperature, fevers have a long list of other causes, including toxins, cancers, and autoimmune diseases.

Heatstroke is a particularly dangerous type of high temperature, because the body is not able to stop the temperature from continuing to rise. It can happen when a child is left in a hot car or when you exercise too strenuously without enough to drink.

Unexplained fevers that continue for days or weeks are referred to by doctors as fevers of undetermined origin (FUO). Most are eventually found to be caused by a hidden infection.

Common Causes Return to top


Viral and bacterial infections
Colds or flu-like illnesses
Sore throats and strep throat
Ear infections
Viral gastroenteritis or bacterial gastroenteritis
Acute bronchitis
Infectious mononucleosis
Urinary tract infections
Upper respiratory infections (such as tonsillitis, pharyngitis or laryngitis)
Medications (such as antibiotics, antihistamines, barbiturates, and drugs for high blood pressure)
Occasionally, more serious problems like pneumonia, appendicitis, tuberculosis, and meningitis
Fever can occur in infants who are overdressed in hot weather or a hot environment
Collagen vascular disease, rheumatoid diseases, and autoimmune disorders
Juvenile rheumatoid arthritis
Lupus erythematosus
Periarteritis nodosa
AIDS and HIV infection
Inflammatory bowel disease
Regional enteritis
Ulcerative colitis
Cancer
Leukemia
Neuroblastoma
Hodgkin's disease
Non-Hodgkin's lymphoma

Home Care Return to top

If the fever is mild and no other problems are present, no medical treatment is required. Drink fluids and rest. If a child is playful and comfortable, drinking plenty of fluids, and able to sleep, fever treatment is not likely to help.

Take steps to lower a fever if you or your child is uncomfortable, vomiting, dehydrated, or having difficulty sleeping. The goal is to lower, not eliminate, the fever.

When trying to reduce a fever:

DO NOT bundle up someone who has the chills.
Remove excess clothing or blankets. The environment should be comfortably cool. For example, one layer of lightweight clothing, and one lightweight blanket to sleep. If the room is hot or stuffy, a fan may help.
A lukewarm bath or sponge bath may help cool someone with a fever. This is especially effective after medication is given -- otherwise the temperature might bounce right back up.
DO NOT use cold baths or alcohol rubs. These cool the skin, but often make the situation worse by causing shivering, which raises the core body temperature.
Drink cool liquids, as tolerated.
Here are some guidelines for taking medicine:
Acetaminophen and ibuprofen help reduce fever in children and adults.
Take acetaminophen every 4-6 hours. It works by turning down the brain's thermostat. Take ibuprofen every 6-8 hours. Like aspirin, it helps fight inflammation at the source of the fever. Sometimes doctors advise you to use both types of medicine. Ibuprofen is not approved for use under 6 months of age.
Aspirin is very effective for treating fever in adults. DO NOT give aspirin to children.
Fever medicines come in different concentrations, so always check the instructions on the package.
Don't use any medicine to reduce fever in children under three months of age without first contacting a physician.
If someone has heat exhaustion or heat stroke, remove the person from the heat source. Sponge the person with tepid water. Place ice packs in the armpits, behind the neck, and in the groin. Give fluids if the person is alert. Seek medical attention. If heat illness is causing the fever, medicines may not lower the body temperature and may even be harmful.

Call your health care provider if Return to top

Call a doctor right away if:

A baby less than 90 days old has a rectal temperature of 100.2°F (37.9°C) or higher.
A baby 3 to 6 months old has a fever of 101°F (38.3°C) or higher.
A baby 6 to 12 months old has a fever of 103°F (39.4°C) or higher.
A child under age two years has a fever that lasts longer than 24 to 48 hours.
A fever lasts longer than 48 to 72 hours in older children and adults.
Anyone has a fever over 105°F (40.5°C), unless it comes down readily with treatment and the person is comfortable.
There are other worrisome symptoms. For example, irritability, confusion, difficulty breathing, stiff neck, inability to move an arm or leg, or first-time seizure.
There are other symptoms that suggest an illness may need to be treated, such as a sore throat, earache, or cough.
You think you may have incorrectly dosed acetaminophen or ibuprofen.
What to expect at your health care provider's office Return to top

Your doctor will perform a physical examination, which may include a detailed examination of the skin, eyes, ears, nose, throat, neck, chest, and abdomen to look for the cause of the fever. Your doctor may ask questions such as.

How long has the fever lasted?
Is it increasing? Is it increasing rapidly?
Has the fever gone away?
How many days did it take for the fever to go away?
Do you have alternating chills and fever?
How frequently does it alternate (days, hours)?
Did it occur within four to six hours after exposure to something that you might be allergic to?
Does the fever follow an up and down pattern (is it high, then lower, then high)?
Did it develop suddenly?
Does the temperature go up and down suddenly (spike) or does it change slowly?
Does it go away and then come back again daily?
Treatment depends on the duration and cause of the fever, and on other accompanying symptoms.

The following diagnostic tests may be performed:

Blood studies, such as a CBC or blood differential
Urinalysis
Sputum culture
Spinal tap
X-ray of the chest

Answer 2

Fever (also known as pyrexia, or a febrile response from the Latin word febris meaning fever, and archaically known as ague) is a frequent medical symptom that describes an increase in internal body temperature to levels that are above normal (37°C, 98.6°F). Fever is most accurately characterized as a temporary elevation in the body’s thermoregulatory set-point, which is usually by about 1-2°C. Fever differs from hyperthermia, which is an increase in body temperature over the body’s thermoregulatory set-point (due to excessive heat production or insufficient thermoregulation, or both).

The elevation in thermoregulatory set-point means that the previous "normal body temperature" is considered hypothermic, and effector mechanisms kick in. The person who is developing the fever has a cold sensation, and an increase in heart rate, muscle tone and shivering attempt to counteract the perceived hypothermia, thereby reaching the new thermoregulatory set-point.

Answer 3

Fever is almost always caused by an underlying infection in the body. (Other causes can be a stroke or a problem with your hypothalamus gland in your brain which functions as your thermometer). Your body temperature rises in attempt to kill the infection among other things that is happening in your body. Dogs and cats also have this response to infection. from, Jill,R.N.

Answer 4

the above answers are correct, but simply put, fever-means your body is trying to fight an invasion of it by a virus, bacteria, rickettsie and so on. Your body is trying to get rid of them, so it raises the temperature. It also is trying to tell you that you are sick, so can take care of it.