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Understanding Pyrexia and Its Causes

Understand pyrexia (fever), its common causes, symptoms, and when it signals a serious condition. Learn how to manage and treat fever effectively in both adults and children.

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Written by Dr. Siri Nallapu

Reviewed by Dr. M L Ezhilarasan MBBS

Last updated on 31st Oct, 2025

Understanding Pyrexia and Its Causes

Understanding Pyrexia and Its Causes

Pyrexia, commonly known as fever, is a condition where your body temperature rises above the normal range (typically 98.6°F or 37°C). While fever is often a sign that your body is fighting an infection, it can also result from other underlying health issues. Understanding pyrexia, its causes, and how to manage it can help you take better care of yourself and your loved ones.

What Is Pyrexia?

Pyrexia is not an illness itself but a symptom of an underlying condition. It occurs when your body’s internal thermostat (the hypothalamus) raises your temperature to help fight infections or respond to other triggers. A mild fever is usually harmless and can even be beneficial, but a very high fever may require medical attention.

Common Symptoms of Pyrexia

  • Elevated body temperature (above 100.4°F or 38°C)
  • Chills or shivering
  • Sweating
  • Headache
  • Muscle aches
  • Fatigue or weakness
  • Loss of appetite
  • Dehydration

In children, fever may also cause irritability, lethargy, or seizures (febrile seizures) in rare cases.

What Causes Pyrexia?

Fever can be triggered by various factors, including:

1. Infections (Most Common Cause)

  • Viral infections (flu, common cold, COVID-19, dengue)
  • Bacterial infections (urinary tract infections, pneumonia, strep throat)
  • Parasitic or fungal infections

2. Inflammatory Conditions

  • Autoimmune diseases (rheumatoid arthritis, lupus)
  • Inflammatory bowel disease (Crohn’s disease, ulcerative colitis)

Consult Top Specialists

Dr. Indrajit Das, General Physician/ Internal Medicine Specialist

Dr. Indrajit Das

General Physician/ Internal Medicine Specialist

4 Years • "MD (Internal medicine) : Gauhati Medical College and Hospital, Guwahati (2018-2021) MD (Pathology) : Gauhati Medical College and Hospital, Guwahati (2012-2015) MBBS (Bachelor of Medicine, Bachelor of Surgery) : Silchar Medical College, Assam (2003-2008) "

Guwahati

Apollo Excelcare Hospital, Guwahati

700

Dr. Mohammed Sharouk Khader, General Physician/ Internal Medicine Specialist

Dr. Mohammed Sharouk Khader

General Physician/ Internal Medicine Specialist

11 Years • MBBS, Bach. of Med. & Surg., Dip. of American Board of Family Med.

Chennai

Apollo Hospitals Greams Road, Chennai

recommendation

99%

(125+ Patients)

1500

Dr. Shoukat Ali Abbas, General Physician/ Internal Medicine Specialist

Dr. Shoukat Ali Abbas

General Physician/ Internal Medicine Specialist

32 Years • MBBS, MD (General Medicine), D. (Diabetology)

Chennai

Apollo Hospitals Greams Road, Chennai

recommendation

93%

(275+ Patients)

1000

1500

Dr. M S Koutilya Choudary, General Physician/ Internal Medicine Specialist

Dr. M S Koutilya Choudary

General Physician/ Internal Medicine Specialist

13 Years • M.B.B.S ,MD

Chennai

Apollo Clinic, Velachery, Chennai

700

700

Dr. Rajib Ghose, General Physician/ Internal Medicine Specialist

Dr. Rajib Ghose

General Physician/ Internal Medicine Specialist

25 Years • MBBS

East Midnapore

VIVEKANANDA SEBA SADAN, East Midnapore

950

850

3. Heat-Related Illnesses

  • Heat exhaustion or heatstroke (due to prolonged exposure to high temperatures)

4. Medications

Some antibiotics, antihistamines, or vaccines can cause a mild fever as a side effect.

5. Other Causes

  • Blood clots
  • Certain cancers
  • Hormonal disorders

When Should You See a Doctor?

Most fevers resolve on their own with rest and hydration. However, seek medical attention if:

Adults:

  • - Fever exceeds 103°F (39.4°C)
  • - Fever lasts more than 3 days
  • - Severe headache, stiff neck, confusion, or difficulty breathing

Children & Infants:

  • - Infants under 3 months with a fever (100.4°F or higher)
  • - Children with a fever above 104°F (40°C)
  • - Fever with rash, seizures, or persistent vomiting

How to Manage Pyrexia at Home?

\Here’s how to manage pyrexia at home:

1. Stay Hydrated

  • Drink plenty of water, herbal teas, or oral rehydration solutions.
  • Avoid caffeine and alcohol, as they can worsen dehydration.

2. Rest

  • Your body needs energy to fight infections, so take adequate rest.

3. Use Fever-Reducing Medications

  • Over-the-counter medicines like paracetamol (acetaminophen) or ibuprofen can help lower fever.
  • Always follow dosage instructions and avoid aspirin for children.

4. Cool Compresses

  • Apply a damp cloth to your forehead or take a lukewarm bath to bring down body temperature.

5. Wear Light Clothing

  • Avoid heavy blankets; opt for breathable fabrics to prevent overheating.

Preventing Fever

While not all fevers can be prevented, you can reduce the risk by:

  • Practising good hygiene (washing hands frequently)
  • Staying up-to-date with vaccinations (flu shot, COVID-19 vaccine)
  • Avoiding close contact with sick individuals
  • Managing chronic conditions (like diabetes or autoimmune disorders)

When to Consult a Doctor?

If your fever persists, worsens, or is accompanied by concerning symptoms, it’s best to consult a healthcare professional. Apollo24|7 offers convenient online consultations and lab tests to help diagnose the cause of persistent fever.

Conclusion

Pyrexia is usually a sign that your body is fighting an infection, and most fevers resolve with simple care. However, persistent or high-grade fever should not be ignored. By staying informed and taking the right steps, you can manage fever effectively and ensure a speedy recovery.


Consult Top Specialists

Dr. Indrajit Das, General Physician/ Internal Medicine Specialist

Dr. Indrajit Das

General Physician/ Internal Medicine Specialist

4 Years • "MD (Internal medicine) : Gauhati Medical College and Hospital, Guwahati (2018-2021) MD (Pathology) : Gauhati Medical College and Hospital, Guwahati (2012-2015) MBBS (Bachelor of Medicine, Bachelor of Surgery) : Silchar Medical College, Assam (2003-2008) "

Guwahati

Apollo Excelcare Hospital, Guwahati

700

Dr. Mohammed Sharouk Khader, General Physician/ Internal Medicine Specialist

Dr. Mohammed Sharouk Khader

General Physician/ Internal Medicine Specialist

11 Years • MBBS, Bach. of Med. & Surg., Dip. of American Board of Family Med.

Chennai

Apollo Hospitals Greams Road, Chennai

recommendation

99%

(125+ Patients)

1500

Dr. Shoukat Ali Abbas, General Physician/ Internal Medicine Specialist

Dr. Shoukat Ali Abbas

General Physician/ Internal Medicine Specialist

32 Years • MBBS, MD (General Medicine), D. (Diabetology)

Chennai

Apollo Hospitals Greams Road, Chennai

recommendation

93%

(275+ Patients)

1000

1500

Dr. M S Koutilya Choudary, General Physician/ Internal Medicine Specialist

Dr. M S Koutilya Choudary

General Physician/ Internal Medicine Specialist

13 Years • M.B.B.S ,MD

Chennai

Apollo Clinic, Velachery, Chennai

700

700

Dr. Rajib Ghose, General Physician/ Internal Medicine Specialist

Dr. Rajib Ghose

General Physician/ Internal Medicine Specialist

25 Years • MBBS

East Midnapore

VIVEKANANDA SEBA SADAN, East Midnapore

950

850

Consult Top Specialists

Dr. Indrajit Das, General Physician/ Internal Medicine Specialist

Dr. Indrajit Das

General Physician/ Internal Medicine Specialist

4 Years • "MD (Internal medicine) : Gauhati Medical College and Hospital, Guwahati (2018-2021) MD (Pathology) : Gauhati Medical College and Hospital, Guwahati (2012-2015) MBBS (Bachelor of Medicine, Bachelor of Surgery) : Silchar Medical College, Assam (2003-2008) "

Guwahati

Apollo Excelcare Hospital, Guwahati

700

Dr. Mohammed Sharouk Khader, General Physician/ Internal Medicine Specialist

Dr. Mohammed Sharouk Khader

General Physician/ Internal Medicine Specialist

11 Years • MBBS, Bach. of Med. & Surg., Dip. of American Board of Family Med.

Chennai

Apollo Hospitals Greams Road, Chennai

recommendation

99%

(125+ Patients)

1500

Dr. Shoukat Ali Abbas, General Physician/ Internal Medicine Specialist

Dr. Shoukat Ali Abbas

General Physician/ Internal Medicine Specialist

32 Years • MBBS, MD (General Medicine), D. (Diabetology)

Chennai

Apollo Hospitals Greams Road, Chennai

recommendation

93%

(275+ Patients)

1000

1500

Dr. M S Koutilya Choudary, General Physician/ Internal Medicine Specialist

Dr. M S Koutilya Choudary

General Physician/ Internal Medicine Specialist

13 Years • M.B.B.S ,MD

Chennai

Apollo Clinic, Velachery, Chennai

700

700

Dr. Rajib Ghose, General Physician/ Internal Medicine Specialist

Dr. Rajib Ghose

General Physician/ Internal Medicine Specialist

25 Years • MBBS

East Midnapore

VIVEKANANDA SEBA SADAN, East Midnapore

950

850

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