What Are The Common Causes Of Fever?

Feeling under the weather? It’s crucial to understand the common causes of fever to decode what your body might be trying to tell you. From viral infections and bacterial infections to autoimmune disorders and certain medications, there are a myriad of factors that can trigger a rise in body temperature. Whether it’s a minor ailment or an indication of a more serious condition, let’s uncover the common culprits behind this universal symptom and gain a better understanding of how fevers come about.


Fever is a common symptom of various infections. Infections can be caused by different types of microorganisms, including bacteria, viruses, fungi, and parasites. Let’s explore each type of infection and how they can lead to fever.

Bacterial Infections

Bacterial infections occur when harmful bacteria invade your body. These infections can cause a wide range of symptoms, including fever. Common examples of bacterial infections include strep throat, urinary tract infections, and pneumonia. When your body detects the presence of bacteria, it triggers an immune response, which includes the release of chemicals that raise your body temperature, resulting in a fever.

Viral Infections

Viruses are tiny organisms that can cause various illnesses, such as the common cold, flu, and COVID-19. When a virus infects your body, it uses your cells to replicate and spread. As your immune system fights against the virus, it releases chemicals called pyrogens, which signal your body to raise its temperature. This elevated body temperature helps your immune system work more efficiently to combat the viral infection.

Fungal Infections

Fungal infections occur when fungi, such as Candida or Aspergillus, invade your body. These infections commonly affect the skin, nails, or mucous membranes. While fungal infections do not typically cause high-grade fevers like bacterial or viral infections, they can still lead to a mild fever or an increase in body temperature. The fever associated with fungal infections is often a result of your immune system’s response to the infection.

Parasitic Infections

Parasitic infections, caused by parasites like malaria parasites or worms, can also be responsible for fever. These tiny organisms live off their hosts and can cause a wide range of symptoms, including fever, as they invade and multiply within the body. In response to the presence of parasites, your immune system activates, which may result in a fever as your body fights against the infection.

Inflammatory Conditions

Apart from infections, there are several inflammatory conditions that can lead to fever. These conditions involve an immune system response that causes chronic inflammation within the body. Here are some examples:

Rheumatoid Arthritis

Rheumatoid arthritis is an autoimmune disease characterized by inflammation of the joints. In addition to joint pain and swelling, people with rheumatoid arthritis may experience fever. This fever is often low-grade, indicating ongoing inflammation within the body.

Crohn’s Disease

Crohn’s disease is a type of inflammatory bowel disease that affects the gastrointestinal tract. Along with symptoms like abdominal pain and diarrhea, individuals with Crohn’s disease may also experience fever. The fever is a result of the chronic inflammation present in the digestive system.

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Ulcerative Colitis

Similar to Crohn’s disease, individuals with ulcerative colitis, another type of inflammatory bowel disease, may experience fever due to the ongoing inflammation in the colon and rectum. Fever is often accompanied by other symptoms such as bloody diarrhea and abdominal cramps.

Systemic Lupus Erythematosus

Systemic Lupus Erythematosus (SLE), commonly known as lupus, is an autoimmune disease that can affect multiple organs in the body. Fever is one of the frequent symptoms experienced by individuals with lupus, particularly during disease flares. The fever in lupus can be associated with various underlying factors, including inflammation and immune system dysfunction.


Certain medications can also cause fever as a side effect. The following classes of drugs are known to potentially induce fever:


Some antibiotics, such as penicillin or sulfa drugs, can cause a drug-induced fever as an allergic reaction. This fever typically occurs shortly after starting the medication and may be accompanied by other symptoms like rash or difficulty breathing. However, not all fevers while taking antibiotics are due to an allergic reaction, so it’s important to consult with your healthcare provider if you suspect a medication-related fever.


Certain antidepressants, such as serotonin-norepinephrine reuptake inhibitors (SNRIs) or monoamine oxidase inhibitors (MAOIs), can cause an increase in body temperature. This is known as serotonin syndrome and can be a serious condition. It is important to notify your healthcare provider if you experience a fever while taking antidepressant medications.

Antiepileptic Drugs

Some antiepileptic drugs, like phenytoin or carbamazepine, have been associated with fever as a potential side effect. If you are taking these medications and experience an unexplained fever, it is crucial to seek medical attention promptly.

Anti-inflammatory Drugs

Nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen or naproxen, are commonly used to reduce inflammation and relieve pain. However, in rare cases, they can cause a hypersensitivity reaction that includes fever. If you develop a fever while taking NSAIDs, it is important to discontinue the medication and consult with your healthcare provider.

Autoimmune Diseases

Autoimmune diseases occur when the immune system mistakenly attacks healthy cells and tissues in the body. Here are some autoimmune diseases that can cause fever:


Systemic Lupus Erythematosus (SLE), or lupus, is an autoimmune disease that can affect various organs and systems in the body. Fever is a common symptom of lupus, particularly during disease flares. The fever in lupus is often a result of the underlying inflammation and immune system dysfunction characteristic of the disease.

Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease primarily affecting the joints. Along with joint pain and swelling, individuals with RA may experience fever. The fever in rheumatoid arthritis can be a result of the persistent inflammation in the joints and other affected tissues.

Hashimoto’s Disease

Hashimoto’s disease is an autoimmune disorder that affects the thyroid gland. It leads to chronic inflammation and the destruction of thyroid tissue. Fever is not a typical symptom of Hashimoto’s disease, but in rare cases, it may occur during disease exacerbations or complications.

Graves’ Disease

Graves’ disease is another autoimmune disorder that affects the thyroid gland. Unlike Hashimoto’s disease, Graves’ disease is characterized by an overactive thyroid gland. Fever is generally not a prominent symptom of Graves’ disease but can occur in severe cases or during thyroid storms, which are sudden and life-threatening exacerbations of the condition.


While cancer itself may not directly cause fever, certain types of cancers or their treatments can lead to fever. Let’s explore some examples:

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Leukemia is a type of cancer that affects the blood and bone marrow. The rapid growth of abnormal white blood cells in leukemia can disrupt normal immune function and lead to fever. In addition, chemotherapy or other anti-cancer treatments can sometimes cause fever as a side effect.


Lymphoma refers to a group of cancers that originate in the lymphatic system, which plays a critical role in the body’s immune response. Fever is a common symptom of lymphoma, particularly in cases of aggressive or advanced disease. As the lymphoma cells grow and spread, the body’s immune response may result in an elevated temperature.

Solid Tumors

Solid tumors can occur in different parts of the body, including the breast, lung, colon, or prostate. While solid tumors themselves may not directly cause fever, certain cancer-related complications, such as infections or inflammation, can lead to an elevated body temperature.

Brain Tumors

Brain tumors can cause a variety of symptoms, including fever. Fever associated with brain tumors may be a result of underlying inflammation or infection. It is essential to seek medical attention if you develop fever along with other neurological symptoms or if your fever persists or worsens.

Heat Exhaustion or Heat Stroke

Apart from infections and medical conditions, external factors such as excessive heat exposure can also lead to fever. Heat exhaustion and heat stroke are two conditions that can result from prolonged exposure to high temperatures. Let’s explore how they can lead to fever:


When you are exposed to high temperatures for an extended period, your body may become dehydrated. Dehydration occurs when there is a significant loss of fluids and electrolytes from your body. This can lead to an increase in body temperature and result in a fever. Staying hydrated and taking regular breaks in a cool environment can help prevent dehydration-related fever.

Prolonged Exposure to High Temperatures

Prolonged exposure to high temperatures without proper hydration and cooling measures can lead to heat exhaustion and, in severe cases, heat stroke. Heat exhaustion typically includes symptoms like dizziness, nausea, and a mildly elevated body temperature. If left untreated, heat exhaustion can progress to heat stroke, where the body’s temperature regulation mechanism fails. Heat stroke is a medical emergency and can result in a high-grade fever, accompanied by other symptoms such as altered mental status and organ failure.

Allergic Reactions

Allergic reactions occur when your immune system overreacts to a substance that is usually harmless. These reactions can cause a variety of symptoms, including fever. Here are some common types of allergic reactions:

Food Allergies

Food allergies occur when your immune system reacts to specific proteins in certain foods. Along with symptoms like hives, swelling, and difficulty breathing, a severe allergic reaction can lead to a fever. It is important to seek immediate medical attention if you suspect a food allergy and develop a fever along with other severe symptoms.

Drug Allergies

Similar to food allergies, drug allergies involve an allergic reaction to medications. Some individuals may develop a drug-induced fever as part of their allergic response. If you experience a fever after taking a medication and suspect it may be due to an allergic reaction, it is crucial to discontinue the medication and seek medical advice promptly.

Insect Allergies

Allergic reactions to insect bites or stings can range from mild to severe. In some cases, a severe allergic reaction, known as anaphylaxis, can occur, leading to symptoms such as difficulty breathing, swelling, and fever. Anaphylaxis is a medical emergency and requires immediate medical attention.

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Hay Fever

Hay fever, also known as allergic rhinitis, occurs when your immune system reacts to allergens in the air, such as pollen or mold spores. While fever is not a typical symptom of hay fever, some individuals may experience a low-grade fever along with other allergic rhinitis symptoms like sneezing, congestion, and itchy eyes.

Hormonal Disorders

Hormonal disorders can also cause fever due to the disruption of normal hormone levels in the body. Here are some examples:

Thyroid Disorders

Thyroid disorders, such as hyperthyroidism or hypothyroidism, can lead to hormonal imbalances and potentially cause fever. In hyperthyroidism, an overactive thyroid gland, fever can occur during severe disease exacerbations or thyroid storms. In hypothyroidism, an underactive thyroid gland, fever is less common but may be seen in rare cases.

Adrenal Insufficiency

Adrenal insufficiency occurs when the adrenal glands do not produce enough hormones, such as cortisol and aldosterone. Along with symptoms like fatigue and weight loss, individuals with adrenal insufficiency may experience fever due to overall hormonal imbalance and impaired stress response.


While fever is not a common symptom of diabetes, very high blood sugar levels, known as diabetic ketoacidosis (DKA), can lead to symptoms that may include fever. DKA is a life-threatening condition typically seen in individuals with uncontrolled diabetes. If you have diabetes and experience a fever, it is essential to monitor your blood sugar levels closely and seek medical attention if necessary.


Some women may experience a mild increase in body temperature during menstruation. This slight elevation in temperature is thought to be related to changes in hormone levels and typically resolves on its own without any medical intervention.

Teething in Infants

Teething refers to the eruption of a baby’s first teeth through the gums. While teething is a natural process, it can cause discomfort and various symptoms, including a mild increase in body temperature. Here are some factors that may contribute to a fever during teething:

Irritation of Gums

As the baby’s teeth begin to push through the gums, it can cause inflammation and irritation. This localized inflammation may result in a slight increase in body temperature, which is generally not a cause for concern. However, if the fever persists or is accompanied by other concerning symptoms, it is important to consult with a pediatrician.

Increased Saliva Production

During the teething process, babies may produce excessive saliva, which can irritate the gums and surrounding tissues. This irritation can lead to mild inflammation and a slightly elevated body temperature. Keeping the baby comfortable and providing appropriate teething aids can help alleviate their discomfort during this time.


Stress, whether physical or emotional, can also contribute to fever. Let’s explore the different types of stress and how they can lead to an increase in body temperature:

Physical Stress

Engaging in strenuous physical activities or experiencing extreme physical exertion can cause the body to generate heat, resulting in an elevated body temperature. This temporary increase in body temperature is often a normal response to physical stress and typically resolves once the stressor is removed, and the body has time to cool down.

Emotional Stress

Emotional stress, such as anxiety or emotional turmoil, can also lead to an increase in body temperature. Stress activates the body’s fight-or-flight response, triggering the release of stress hormones like cortisol, which can influence body temperature regulation. While mild emotional stress may cause a temporary, mild increase in temperature, persistent or severe stress should be addressed with appropriate coping mechanisms and support.

In conclusion, fever can be caused by a wide range of factors, including various infections, inflammatory conditions, medications, autoimmune diseases, cancer, heat-related conditions, allergic reactions, hormonal disorders, teething in infants, and stress. It is important to pay attention to accompanying symptoms, the duration of the fever, and seek medical advice if necessary. Remember, if you or someone you know is experiencing a high-grade or persistent fever, it is best to consult with a healthcare professional for a proper evaluation and guidance.