Fever is the elevation of body temperature beyond what is normal. It is not a disease in itself but is a sign of an underlying condition. A fever usually indicates that the body is battling an inflammation that could be due to an infection, vaccination, immune reaction, or other causes. Although it causes some discomfort, a fever is actually a protective mechanism of the body to fight off infection or other foreign invaders of the body.

A fever is identified by taking the body temperature using a thermometer, which can be either digital or made of glass and mercury. In most countries, mercury thermometers are no longer used because of the risk of breaking the glass and spilling mercury (a toxic substance) to the environment. In most countries, the digital thermometer is the preferred device not only because it is safer but also because it registers temperature faster.

Several areas of the body can be used to measure the body temperature. The ears, forehead, mouth, armpit, and rectum can all be used for this purpose. Among all these parts, the rectum is the least accessible but is the most accurate area to measure the temperature. Fever is defined as:

  • Rectal temperature higher than 100.4°F (38°C)
  • Oral temperature higher than 100°F (37.8°C)
  • Ear temperature higher than 100.4°F (38°C)
  • Forehead temperature higher than 100.4°F (38°C)
  • Armpit temperature higher than 99°F (37.2°C)


Whenever a person develops fever, it is usually associated with other symptoms. Fever is rarely a lone sign. It usually comes with other signs and symptoms that give clues as to the actual cause of fever. The following are some of the common causes of fever:

  • Infection: Bacterial, viral, parasitic, or fungal infections can cause fever. Bacterial infections include pneumonia, bronchitis, meningitis, UTI, abscesses, and others. Examples of viral infections are flu, colds, mumps, measles, among others. All of these infections can present with fever.
  • Inflammation or immune response: Inflammation or immune response of the body can be triggered even without an infection. Examples of inflammatory conditions that can be accompanied with fever are rheumatoid arthritis, systemic lupus, and sarcoidosis. A very common example of an immune response that can trigger fever is vaccination, especially in children.
  • Toxins: Toxic chemicals like poison, spoiled food or venom from some animals can cause fever.
  • Cancer: Tumor fever is a common condition among cancer patients wherein the cancer cells release chemicals that trigger the cascade of reactions for fever.
  • Medications: Some drugs can cause fever especially if there is a component of the drug that a person is allergic or sensitive to.

When to seek consult

Ideally, all individuals who develop fever should be brought to the doctor for an examination. More so, individuals with the following signs and symptoms should be brought to the doctor IMMEDIATELY:

  • Fever that is 104°F (40°C) or higher
  • Fever associated with convulsions
  • Fever with rash
  • Fever with bleeding
  • Fever with abdominal pain
  • Fever in a patient undergoing chemotherapy
  • Fever in an infant (<3 months), no matter how normal or active the infant appears


To diagnose the underlying cause of fever, the doctor will perform a thorough history and physical examination of the patient. After that, the doctor might request for additional tests depending on his suspicions. Some of these tests are:

  • Complete blood count
  • Urinalysis and possible cultures (done to grow the organism)
  • Fecalysis and possible cultures
  • Chest X-ray
  • Other blood chemistries and possible cultures


The treatment of fever depends on the underlying cause. For example, infections are treated with antibiotics, anti-virals, anti-fungals or anti-parasitics depending on the etiologic agent. Inflammatory diseases are controlled with steroids and anti-inflammatory drugs. Tumor fever is treated with anti-inflammatory drugs. Drug fever is treated by stopping the medication that causes the fever.

Fever, per se, can be addressed by medications called anti-pyretics. Examples of these medications are acetaminophen and ibuprofen (NSAIDS). Other supportive treatments for fever include drinking fluids to avoid dehydration, rest, and sponge baths to lower the body temperature.

Aspirin, a common pain medication, should not be given to children because it can cause Reye’s syndrome. Reye’s syndrome is a rare but potentially fatal condition that is characterized by rashes, seizures and confusion due to the swelling of the brain and the liver.