Understanding the Hidden Reasons: What Is the Reason Why My Fever Keeps Coming Back?

September 30, 2025 •

4 min read

According to the Better Health Channel, a fever is a temporary rise in body temperature often caused by an infection. However, when a fever keeps coming back, it signals an unresolved issue within the body, which requires a closer look at a variety of potential underlying causes.

Quick Summary

Recurring fevers can stem from a range of issues, including persistent or chronic infections, autoimmune disorders, or systemic autoinflammatory diseases. Other potential causes include certain medications, malignancies, and environmental factors. A healthcare provider can help diagnose the root cause.

Key Points

Persistent Infections: Unresolved bacterial, viral, or parasitic infections can cause fevers to keep coming back until the underlying pathogen is completely eliminated or managed.
Autoimmune Disorders: Chronic conditions like lupus or rheumatoid arthritis can trigger recurring fever during flare-ups as the immune system attacks healthy tissue.
Autoinflammatory Syndromes: Genetic disorders, such as Familial Mediterranean Fever (FMF), cause cycles of unexplained fever and inflammation that are not due to infection.
Medication Side Effects: A side effect known as drug fever can cause intermittent fevers that resolve once the offending medication is discontinued.
Malignancies and Chronic Illnesses: In rare cases, certain cancers or poorly managed chronic diseases can cause recurrent fevers, signaling a need for further investigation.
Professional Diagnosis is Key: The pattern of the fever, accompanying symptoms, and family history are crucial clues that a healthcare provider uses to diagnose the specific underlying cause.

Infections: The Most Common Culprits

Infections are the most common cause of fever, and a recurrent or intermittent fever can signal an infection that is chronic, unresolved, or relapsing.

Chronic Bacterial Infections: Sometimes, bacterial infections are not completely eradicated by a course of antibiotics, leading to a recurrence of symptoms. Examples include tuberculosis, urinary tract infections (UTIs), and certain types of abscesses.
Relapsing Viral Infections: Some viruses can persist in the body and reactivate later, causing new bouts of fever. The Epstein-Barr virus (mononucleosis) is a classic example.
Parasitic Infections: In regions where they are common, parasitic diseases like malaria can cause cyclical fevers that come and go at regular intervals, often accompanied by chills and fatigue.
Fungal Infections: In rare cases, systemic fungal infections can also trigger recurring fevers that resist standard treatment.

Autoimmune and Inflammatory Conditions

When the immune system malfunctions, it can mistakenly attack healthy tissues, leading to chronic inflammation and recurring fever episodes.

Autoimmune Diseases: Conditions like systemic lupus erythematosus (lupus) and rheumatoid arthritis involve the adaptive immune system attacking the body's own cells. The resulting inflammation can trigger flare-ups that include fevers.
Systemic Autoinflammatory Diseases (SAIDs): These are a group of genetic disorders involving a dysregulation of the innate immune system. Unlike autoimmune diseases, SAIDs are not caused by the immune system mistakenly targeting a specific tissue but rather by unprovoked, systemic inflammation.
- Familial Mediterranean Fever (FMF): The most common SAID, often seen in people of Mediterranean descent, causes episodes of fever, abdominal pain, chest pain, and joint pain.
- Periodic Fever, Aphthous Stomatitis, Pharyngitis, and Adenitis (PFAPA) Syndrome: Affecting mostly children, PFAPA causes recurrent high fevers accompanied by mouth sores, a sore throat, and swollen lymph nodes.
- Tumor Necrosis Factor Receptor-Associated Periodic Syndrome (TRAPS): This genetic condition can cause fever episodes lasting weeks, along with muscle pain, a painful rash, and swelling around the eyes.

Medication-Induced and Other Rare Causes

Sometimes, the cause of a recurring fever is not an infection or disease but a side effect of medication or another underlying issue.

Drug Fever: Almost any medication can cause a fever as an adverse reaction, but it is particularly associated with antimicrobials. The fever typically subsides within 48 to 72 hours of discontinuing the drug.
Malignancies (Cancer): In rare instances, particularly with certain types of lymphomas or leukemia, a recurring fever can be a symptom. The fever may be accompanied by other symptoms like unexplained weight loss or night sweats.
Poorly Managed Chronic Conditions: In individuals with conditions like uncontrolled diabetes or kidney disease, a weakened immune system can make them more susceptible to repeated infections.

Diagnosing the Cause of Recurrent Fevers

When facing a recurring fever, a healthcare provider will conduct a thorough investigation to pinpoint the cause. This process involves a detailed history, physical examination, and various tests.

Medical History: The doctor will ask about the pattern of the fever, its duration, accompanying symptoms, family history, and any recent travel or medication changes.
Physical Examination: A physical exam can reveal important clues, such as rashes, swollen lymph nodes, or signs of inflammation in the joints.
Diagnostic Testing: Blood and urine tests are often performed to check for signs of infection or inflammation. In some cases, genetic testing may be used to confirm a diagnosis of an autoinflammatory syndrome.

Comparison of Recurrent Fever Causes


Feature	Infectious Causes	Autoimmune Conditions	Autoinflammatory Syndromes
Mechanism	Body fighting a persistent, chronic, or relapsing pathogen.	Adaptive immune system attacks the body's own tissues.	Innate immune system is dysregulated, causing unprovoked inflammation.
Common Examples	Tuberculosis, malaria, chronic UTIs, reactivated viral infections (EBV).	Systemic lupus erythematosus, rheumatoid arthritis.	PFAPA syndrome, Familial Mediterranean Fever (FMF), TRAPS.
Typical Pattern	Can vary widely; may be persistent, intermittent, or cyclical depending on the pathogen.	Often occurs during a "flare-up" alongside other systemic symptoms.	Predictable, cyclical episodes of fever with periods of feeling well in between.
Diagnostic Markers	Pathogen-specific tests, elevated white blood cells.	Presence of autoantibodies (e.g., ANA), inflammatory markers (CRP, ESR).	Genetic testing for specific mutations; elevated inflammatory markers during episodes.

Conclusion

Recurrent fever is a signal that should not be ignored. While common infections are frequent culprits, the possibility of an underlying autoimmune disease, autoinflammatory syndrome, or other condition makes a professional medical evaluation essential. A detailed history and targeted diagnostic testing can help uncover the true reason for the returning fever. By working with a healthcare provider, the underlying cause can be identified and a targeted treatment plan can be put in place to manage symptoms, prevent complications, and restore overall well-being.

Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice. Always consult a qualified healthcare provider for diagnosis and treatment of any health condition.

Frequently Asked Questions

If a fever persists for several days, reaches 103°F (39.4°C) or higher in adults, or is accompanied by other severe symptoms, you should seek immediate medical attention. For recurrent fevers of unknown cause, a medical evaluation is warranted to rule out underlying conditions.

The contagiousness depends on the underlying cause. If the fever is due to a viral or bacterial infection, it may be contagious. However, fevers caused by autoimmune disorders, autoinflammatory syndromes, or medications are not contagious.

Autoimmune diseases involve a malfunction of the adaptive immune system, which mistakenly attacks the body's own tissues (e.g., lupus). Autoinflammatory diseases involve a dysregulation of the innate immune system, causing unprovoked, systemic inflammation (e.g., PFAPA syndrome).

While stress does not cause a true, sustained fever, it can influence body temperature regulation. In individuals with pre-existing inflammatory conditions like FMF, stress can sometimes trigger a fever episode.

To diagnose the cause, a doctor may order blood tests (like CRP, ESR, and white blood cell count), urine tests, genetic tests, and possibly imaging studies. These tests help check for infection, inflammation, and potential genetic factors.

Yes, allergic reactions, especially drug or food allergies, can sometimes cause intermittent fevers. Exposure to certain environmental toxins, such as toxic mold, has also been listed as a potential factor.

PFAPA stands for Periodic Fever, Aphthous Stomatitis, Pharyngitis, and Adenitis. It is a common benign autoinflammatory syndrome in children that causes episodes of high fever, mouth sores, sore throat, and swollen lymph nodes. It often resolves on its own by age 10.