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40 Causes of Fever

Fevers could be caused by a multitude of reasons, from a very simple one to an extremely complicated and even dangerous one. Many of us think or are made to think that “a fever” is a disease by itself which is quite far from the truth.

The temporary considerable rise in body temperature above the average normal of 37° Celsius (98.6° Fahrenheit) is called a fever and depending on the degree of rise it is categorized as mild, medium or high. Anything above the armpit temperature reading of 37.2°C (99°F) or oral temperature reading of 37.8°C (100°F) is an indication of a fever.

Alternatively you could say, a fever is the temporary rise in temperature of the body when the body’s cells are fighting or reacting to an infection or threat caused to it by one or many of the reasons mentioned below.


  1. Autoimmune conditions – An autoimmune disease is a condition in which your immune system mistakenly attacks your body. In an autoimmune disease, the immune system mistakes part of your body, like your joints or skin, as foreign. It releases proteins called autoantibodies that attack healthy cells. Some autoimmune diseases target only one organ. Type 1 diabetes damages the pancreas. Other diseases, like systemic lupus erythematosus (SLE), affect the whole body. Often, the first symptoms are fatigue, muscle aches and a low fever.
  2. TraumaTrauma is an emotional response to a terrible event like an accident, rape or natural disaster. Immediately after the event, shock and denial are typical. Longer term reactions include unpredictable emotions, flashbacks, strained relationships and even physical symptoms like headaches or nausea. Fever is strongly associated with poor outcome after traumatic brain injury (TBI).
  3. Inflammatory condition – Inflammatory diseases include a vast array of disorders and conditions that are characterized by inflammation. Examples include allergy, asthma, autoimmune diseases, coeliac disease, glomerulonephritis, hepatitis, inflammatory bowel disease, preperfusion injury and transplant rejection. Autoimmune and autoinflammatory diseases are both lifelong conditions that cause fever, pain, swelling and inflammation.
  4. Sudden shock – In medical terms, shock is the body’s response to a sudden drop in blood pressure. A drop in blood pressure reduces the flow of oxygen and nutrients to a person’s vital organs such as their brain, heart and lungs. If the blood flow is not restored, the person may die from complications due to lack of oxygen supply to major organs (hypoxia). Symptoms of septic shock include fever, nausea, vomiting, and dizziness or fainting.
  5. Antibiotics – Fevers are a common side effect of many medications, including antibiotics. A fever may occur because of an allergic reaction to a medication or as a bad side effect. Drug fevers can occur with any antibiotic.
  6. Stroke – Approximately 50% of patients hospitalized for stroke develop fever. In fact, experimental evidence suggests that high body temperature is significantly correlated to initial stroke severity, lesion size, mortality, and neurologic outcome. Fever occurring after stroke is associated with poor outcomes.
  7. Brain tumor – A cancer may also cause symptoms like fever, extreme tiredness (fatigue), or weight loss. This may be because cancer cells use up much of the body’s energy supply, or they may release substances that change the way the body makes energy from food. 
  8. Lung conditions – Exposure of the lungs to airborne toxicants from different sources in the environment may lead to acute and chronic pulmonary or even systemic inflammation. Cigarette smoke is the leading cause of chronic obstructive pulmonary disease, although wood smoke in urban areas of underdeveloped countries is now recognized as a leading cause of respiratory disease. Mycotoxins from fungal spores, microscopic airborne particulates of asbestos and silica (from building materials) and those of heavy metals (from paint) also cause inflammation of the lungs. Most if not all lung inflammations are accompanied by fever.
  9. ARDS – is a type of respiratory failure characterized by rapid onset of widespread inflammation in the lungs. The most common cause of ARDS is sepsis, a serious and widespread infection of the bloodstream. Inhalation of harmful substances. Breathing high concentrations of smoke or chemical fumes can result in ARDS, as can inhaling (aspirating) vomit or near-drowning episodes.
  10. Allergy – Allergies can cause symptoms that are very similar to a cold or flu, such as a runny nose, sore throat, or sneezing. With allergies, you will run a low-grade fever of 100.1 or 100.2 F.
  11. Pancreatitis – Common causes of pancreatitis are gallstones or alcohol abuse. Sometimes no cause for pancreatitis can be found. Symptoms of acute pancreatitis include pain in the abdomen, nausea, vomiting, fever, and a rapid pulse.
  12. Gallstone – Cholecystitis can cause severe pain and fever. Blockage of the common bile duct. Gallstones can block the tubes (ducts) through which bile flows from your gallbladder or liver to your small intestine.
  13. Kidney stone – Kidney stones or renal calculus can cause much pain and discomfort, especially when the warning signs are ignored. Fevers can be caused due to the severe pain or the on-set of infection.
  14. Thyroid storm – Thyroid storm is a life-threatening health condition that is associated with untreated or under-treated hyperthyroidism. During thyroid storm, an individual’s heart rate, blood pressure, and body temperature can soar to dangerously high levels.
  15. Gout – When gout occurs, the joint tends to be extremely painful and is warm, red and swollen. The inflammation that is part of a gout attack is systemic, so that fever and chills, fatigue and malaise are not uncommonly part of the picture of a gout attack.
  16. Virus – A viral fever is caused by infection with a virus. Viruses are very small infectious agents. They infect and multiply within the cells of your body.You get a fever because your body is trying to kill the virus or bacteria that caused the infection.
  17. Bacterial infection – A variety of bacterial infections can cause FUO, and these can be divided into those that are easy to identify using culture and those that require serological or molecular tests for identification.
  18. Heat exhaustion – Heat exhaustion can occur if your body temperature increases and you’re not able to cool yourself down quickly enough. This may happen in high temperatures, such as those experienced during the summer months. It can cause mild fever.
  19. Certain inflammatory conditions such as rheumatoid arthritis — inflammation of the lining of your joints (synovium), crohn’s disease
  20. Drugs for High Blood pressure – Some possible side effects of high blood pressure medicines include: Chest pain, heart palpitations (the feeling that your heart is racing), or arrhythmia (irregular heartbeat), cough, fever, congestion, upper respiratory tract infection, or flu-like symptoms.
  21. Familial Dysautonomia – Infants with this disorder may have cold hands and feet and experience unstable body temperature (from 94 to 108 degrees) during the course of infectious diseases. Profuse sweating and drooling may also occur. Crying without tears is one of the most striking symptoms of familial dysautonomia.
  22. Some vaccines, such as the diphtheria, tetanus and acellular pertussis (DTaP) or pneumococcal vaccine – Many people who receive vaccines have no side effects. For those that do, the side effects are usually very minor, like soreness, redness, or swelling where the vaccine was given, or a mild fever. Some people might have a more serious reaction to a vaccine, like a high fever which can in turn cause febrile seizures.
  23. Overexposing the skin to sunlight, or sunburn – If your skin breaks out in itchy bumps or painful blisters in areas that have been exposed to sun, you may be experiencing sun poisoning, which is more severe than the typical sunburn. Other symptoms of sun poisoning include fever, chills, and nausea. 
  24. Heatstroke, either due to high ambient temperatures or prolonged strenuous exercise – Heat exhaustion when untreated causes heat strokes with Fever of 104°F or higher, Flushed or red skin, Lack of sweating, Trouble breathing, Fainting, Seizures
  25. Dehydration – When your body doesn’t have enough fluids, it’s hard to maintain a regular body temperature and this can lead to hyperthermia and fever-like symptoms including chills.
  26. Silicosis – which is a type of lung disease caused by long-term exposure to silica dust –  Silicosis (particularly the acute form) is characterized by shortness of breath, cough, fever, and cyanosis (bluish skin). It may often be misdiagnosed as pulmonary edema (fluid in the lungs), pneumonia, or tuberculosis. Silicosis resulted in 46,000 deaths globally in 2013, down from 55,000 deaths in 1990.
  27. Amphetamine or cocaine abuse – use and abuse of amphetamines can cause the body temperature to rise.
  28. Alcohol withdrawal – Alcohol withdrawal syndrome is a set of symptoms that can occur following a reduction in alcohol use after a period of excessive use. Symptoms typically include anxietyshakiness, sweating, vomiting, fast heart rate, and a mild fever.
  29. Infections of the ear, lungskin, throat, bladder, or kidney – caused by damage or otherwise is highly likely to be followed by a fever ranging from low to medium.
  30. Cancer – People who have cancer will often have a fever as a symptom. It’s usually a sign that the cancer has spread or that it’s in an advanced stage.
  31. Blood clots – When a blood clot breaks and enters the bloodstream, it can cause your body temperature to spike. Look out for a fever with a sudden onset.
  32. Hormone disorders such as hyperthyroidism – Too much thyroid hormone can prevent your body from absorbing calcium into your bones. A sudden worsening of hyperthyroidism symptoms that leads to a fever, rapid pulse, and delirium.
  33. Food poisoning – Food poisoning, also called food-borne illness, is illness caused by eating contaminated food. Infectious organisms — including bacteria, viruses and parasites — or their toxins are the most common causes of food poisoning. The most common symptoms of food poisoning are: Upset stomach, Stomach cramps, Nausea, Vomiting, Diarrhea, Fever
  34. Urinary tract infection – Infection in the upper urinary tract generally affects the kidneys (pyelonephritis), which can cause fever, chills, nausea, vomiting, and other severe symptoms. The lower urinary tract consists of the bladder and the urethra.
  35. Mononucleosis – Often called mono or kissing disease, an infection with the Epstein-Barr virus. Mono (glandular fever) is transmitted by saliva. Symptoms include fatigue, fever, rash and swollen glands. The elderly may not have typical symptoms.
  36. Menstruation – Flu-like symptoms such as headache, nausea, and even fever are just some of the complaints that have people wondering if they’re getting sick or going crazy during that time of the month.
  37. Granulomatous diseases – Chronic granulomatous (gran-u-LOM-uh-tus) disease (CGD) is an inherited disorder that occurs when a type of white blood cell (phagocyte) that usually helps your body fight infections doesn’t work properly. As a result, the phagocytes can’t protect your body from bacterial and fungal infections. Individuals with chronic granulomatous disease may develop a type of fungal pneumonia, called mulch pneumonitis, which causes fever and shortness of breath after exposure to decaying organic materials such as mulch, hay, or dead leaves.
  38. Vasculitis – is inflammation of your blood vessels. It causes changes in the blood vessel walls, including thickening, weakening, narrowing or scarring. Patients with vasculitis often have fevers, weight loss, fatigue, a rapid pulse, and diffuse aches and pains that are difficult to pinpoint.
  39. Intracerebral hemorrhage (ICH) – is caused by bleeding within the brain tissue itself — a life-threatening type of stroke. A stroke occurs when the brain is deprived of oxygen and blood supply. ICH is most commonly caused by hypertension, arteriovenous malformations, or head trauma. Fever is common after an intracerebral hemorrhage.
  40. Blood product transfusion – Fever and chills during transfusion are thought to be caused by recipient antibodies reacting with white cell antigens or white cell fragments in the blood product or due to cytokines which accumulate in the blood product during storage.