What Is Fever? What Causes Fever?

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Main Category: Public Health
Also Included In: Primary Care / General Practice;  Pediatrics / Children's Health;  Infectious Diseases / Bacteria / Viruses
Article Date: 22 Oct 2009 - 0:00 PST

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Fever is a common medical sign that describes an increase in internal body temperature to levels above normal. Generally, a fever is an indication of something unusual in the body. It is the body's response to a disease. In adults, a fever usually is not dangerous unless it reaches 103 F (39.4 C) or higher. In young children and infants, a slightly elevated temperature may be a sign of a serious infection.

According to Medilexicon's medical dictionary, fever is: "A complex physiologic response to disease mediated by pyrogenic cytokines and characterized by a rise in core temperature, generation of acute phase reactants, and activation of immune systems."

The degree of fever is not necessarily related to the seriousness of the underlying condition. There are numerous over-the-counter medications to lower a fever. However, it seems sometimes it is better left untreated. Fever could play an important role in helping the body fight off a number of infections. Fever is considered as one of the body's immune mechanisms to attempt a neutralization of a perceived threat inside the body (bacterial or viral).

What are the signs and symptoms of fever?

A symptom is something the patient reports and feels, while a sign is something other people, including a doctor may detect. For example, a headache may be a symptom while a rash may be a sign.

The average temperature of the human body is 98.6 F (37 C).

Depending on the cause of the fever, symptoms may include:

• Dehydration
• General weakness
• Headache
• Inability to concentrate
• Loss of appetite
• Muscle aches
• Sweating
• Trembling, shivering

High fevers between 103 F (39.4 C) and 106 F (41.1 C) may cause:

• Confusion
• Convulsions
• Hallucinations
• Irritability

Fever-induced seizures in children

In some cases, children younger than age 5 can experience fever-induced seizures or febrile seizures. When a child's temperature rises or falls rapidly febrile seizures can occur. The signs include convulsions and a brief loss of consciousness.

Although alarming, these seizures usually do not cause any lasting effects and are often triggered by a fever from a common childhood illness.

Infants

An unexplained fever is greater cause for concern in infants and in children than in adults. It is recommended to seek medical advice when a baby has a fever of 101 F (38.3 C) or higher or when:

• The baby is younger than 3 months of age.


• Infant refuses to eat or drink.


• Has a fever and unexplained irritability. Unusual crying during a diaper change or when moved.


• Has a fever and seems lethargic and unresponsive. In infants and children younger than age 2, these may be signs of meningitis (an infection and inflammation of the membranes and fluid surrounding the brain and spinal cord).


• When a newborn and has a lower than normal temperature. Less than 97 F (36.1 C). Very young babies may not be able to regulate their body temperature when they are ill. They may become cold rather than hot.

Children

Children usually tolerate fevers well. Parents should not only check temperature measurement but also how the child behaves. There is probably no cause for alarm if the child has a fever but is responsive, drinking fluids, playing, making eye contact and responding to stimuli such as facial expressions and voice. Seek medical advice if the child:

• Has a fever after being left in a hot car. Seek medical care immediately.


• Has a fever that persists longer than one day in children younger than age 2. Fever lasting longer than three days in children ages 2 and older.


• Is lethargic or irritable, vomits repeatedly, has a severe headache or stomachache, or has any other symptoms causing major discomfort.

Ask for medical guidance if there are special circumstances (a child with immune system problems or with a pre-existing illness).

Sometimes, older children with severe neurological impairments, with a life-threatening bacterial infection in the blood (sepsis) or with suppressed immune systems can have a lower than normal temperature.

Adults

Seek medical advice if:

• Temperature is higher than 103 F (39.4 C)
• There is fever for more than three days

In addition, seek immediate medical attention if a fever appears together with any of these signs or symptoms:

• Abdominal pain or pain when urinating
• Difficulty breathing or chest pain
• Extreme lethargy or irritability
• Mental confusion
• Persistent vomiting
• Severe headache
• Severe throat swelling
• Stiff neck and pain when bending head forward
• Unusual sensitivity to bright light
• Unusual skin rash, especially if the rash rapidly worsens
• Any other unexplained signs or symptoms

What are the causes of fever?

There are many variations in normal body temperature, and this needs to be considered when measuring fever. Normal body temperature varies throughout the day according to circadian rhythm. It is lower in the morning and higher in the late afternoon and evening. Normal temperature can range from about 97 F (36.1 C) to 99 F (37.2 C). However, 98.6 F (37 C) is generally considered normal. Temperature is increased after eating, and psychological factors also influence body temperature. Other factors, such as menstrual cycle or heavy exercise, can have an effect.

The mechanism of body temperature:

• Body temperature is set by the hypothalamus which is an area at the base of the brain that acts as a thermostat for the whole system.


• Temperature is the balance of the heat produced by the body tissues (particularly the liver and muscles), and the heat the body loses.


• During illness, normal temperature may be set a little higher as the body directs blood away from the skin to decrease heat loss.


• When a fever starts, the body tries to elevate its temperature. There is a feeling of chilliness and possible shivering. This is to generate heat until the blood around the hypothalamus reaches the new set point.


• When temperature begins to return to normal, there may be profuse sweat to get rid of the excess heat.


• For the very old, the very young or alcoholic, the body's ability to produce a fever may be diminished.

Usually, a fever indicates the body is responding to a viral or bacterial infection. Other possible causes include:

• Certain inflammatory conditions such as rheumatoid arthritis (inflammation of the lining of the joints)


• Extreme sunburn


• Heat exhaustion


• In some rare cases, a malignant tumor or some forms of kidney cancer


• Some immunizations, such as the diphtheria, tetanus and acellular pertussis (DTaP) or pneumococcal vaccines (in infants and children)


• Some medications, such as antibiotics and drugs used to treat high blood pressure or seizures

Sometimes it is impossible to identify the cause of a fever. If a temperature of 101 F (38.3 C) or higher lasts for more than three weeks and it is medically impossible to find the cause after extensive evaluation, the diagnosis may be fever of unknown origin.

How is fever diagnosed?

Put simply, diagnosing a fever is simple - if the patient's body temperature is higher than normal when they are sedentary (not running around, just sitting or lying down), they have a fever. Depending on other signs and symptoms, a physical examination, and possibly some other tests, the physical will determine whether the cause is an infection or something else.

To confirm a diagnosis, other tests may be required, such as blood tests.

In the case of a low-grade fever that persists for three weeks or more, but with no other symptoms, a variety of tests may be recommended to help find the cause. These may include blood tests and X-rays.

What is the treatment for fever?

Treatment depends on the cause of the fever. Antibiotics will be prescribed for bacterial infections, such as pneumonia or strep throat.

Antibiotics do not treat viral infections, such as stomach infection and mononucleosis. There are a few antiviral drugs used to treat some specific viral infections. However, the most effctive treatment for most viruses is often rest and plenty of fluids.

Over-the-counter medications

Over-the-counter medications may be recommended, such as acetaminophen (Tylenol, parecetamol) or ibuprofen (Advil, Motrin) to lower a high fever. Adults also may use aspirin. However, do not give aspirin to children under 16 years of age, because it may trigger a rare, but potentially fatal, disorder known as Reye's syndrome.

Is it wise to lower a fever?

In the case of a low-grade fever, it is not advisable to try to lower the temperature. This may extend the illness or mask symptoms and make it more difficult to determine the cause.

A number of experts judge that aggressively treating a fever interferes with the body's immune response. The viruses that cause colds and other respiratory infections thrive at normal body temperature. By producing a low-grade fever, the body may be helping eliminate a virus.

What are the complications of fever?

A fast rise or fall in temperature may cause a fever-induced seizure (febrile seizure) in a small number of children aged from 6 months to 5 years. Although alarming, the vast majority of febrile seizures cause no long-lasting effects.

Febrile seizures usually involve loss of consciousness and shaking of limbs on both sides of the body. Infrequently, a child may become rigid and convulse only part of his or her body.

What to do in case of a febrile seizure?

Lay the child on his or her side or stomach on the floor or ground. Remove any sharp objects that are near the child, loosen tight clothing and hold the child to prevent injury. Do not place anything in the child's mouth or try to stop the seizure. Although most seizures stop on their own, call for emergency medical assistance if a seizure lasts longer than 10 minutes.

After the seizure, take the child to the doctor as soon as possible to determine the cause of the fever.

Remedies

A number of things can be of assistance during a fever:

• Drinking plenty of fluids. Drinking water, juices or broth. Fever can cause fluid loss and dehydration. The use an oral rehydration solution (such as Pedialyte) is recommended for a child under age 1.


• Resting. It is essential for recovery. Activity can raise body temperature.


• Staying cool. Dressing in light and comfortable clothing, keeping the room temperature cool.


• Taking acetaminophen or ibuprofen. Use according to the instructions or doctor's recommendations. High doses or long-term use of acetaminophen may cause liver or kidney damage, and acute overdoses can be fatal.


• Soaking in lukewarm water. Particularly in case of high temperatures, a lukewarm five- to 10-minute soak or bath can be cooling. Do not use alcohol. And if the bath causes shivering, stop the bath. Shivering raises the body's internal temperature (shaking muscles generate heat).

Taking a temperature

Fever is present if:

• Temperature in the anus (rectum/rectal) is at or over 100.0 °F (37.8 °C)
• Temperature in the mouth (oral) is at or over 99.5 °F (37.5 °C)
• Temperature under the arm (axillary) is at or over 99.0 °F (37.2 °C)
• Temperature in the ear is at or over 99.0 ºF (37.2 ºC)

To check temperature, there are several types of thermometers, including electronic thermometers and ear thermometers. Digital thermometers and those that quickly take temperature from the ear canal are particularly useful for young children and older adults. As glass mercury thermometers may have potential health implications for humans and the environment, they have been discontinued and are no longer recommended. Although not the most accurate way to take a temperature, oral thermometer can be used for an armpit reading:

• Place the thermometer in the armpit with arms crossed over the chest.


• Wait four to five minutes. The axillary temperature is slightly lower than an oral temperature.


• The actual number on the thermometer should be reported to the doctor. Specify where on the body the temperature taken.

Use a rectal thermometer for infants:

• Place a dab of petroleum jelly on the bulb.


• Lay baby on his or her tummy.


• Carefully insert the bulb one-half inch to one inch into the baby's rectum.


• Hold the bulb and baby still for three minutes.


• Do not let go of the thermometer while it is inside the baby. If the baby moves, the thermometer could go deeper and cause an injury.

How to prevent fever?

It is possible to prevent fever by reducing exposure to infectious diseases. The most simple and effective way is frequent hand washing for adults and children.

Washing hands often, especially before eating and after using the toilet, after spending time in a crowd or around someone who's sick, and after petting animals. Show children how to wash their hands properly, lathering both the front and back of each hand with soap, and rinsing carefully under running water. When there is no access to soap and water, carrying moist towelettes or hand sanitizer. When possible, trying not to touch nose, mouth or eyes which are the main way viral infections are transmitted.

In addition, adults and children should remember to turn away from others and to cover their mouths when coughing and their noses when sneezing.

Written by Stephanie Brunner B.A.
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today