Fever

Fever occurs when your body's thermostat (located in the hypothalamus) resets to a higher temperature. This is usually triggered by substances called pyrogens, which can be produced by bacteria, viruses, or your own immune cells. The elevated temperature creates an environment less favorable for pathogens and enhances immune function.

Normal body temperature varies throughout the day, typically lowest in the early morning and highest in the late afternoon. It also varies between individuals and can be affected by age, activity level, and hormonal changes. What constitutes a fever can depend on how temperature is measured - oral, rectal, ear, or forehead readings can differ slightly.

While fever is often associated with feeling unwell, the fever itself is rarely harmful. In fact, moderate fever may help the body fight infection more effectively. However, very high fevers or prolonged fevers can be dangerous and require medical attention.

Infectious Causes

Viral Infections

• Influenza (Flu): High fever, body aches, fatigue
• COVID-19: Fever with cough, loss of taste/smell
• Common cold: Usually low-grade fever
• Gastroenteritis: Stomach flu with fever, vomiting, diarrhea
• Chickenpox: Fever with characteristic rash
• Mononucleosis: Prolonged fever with fatigue, sore throat

Bacterial Infections

• Pneumonia: Fever with cough, chest pain
• UTI: Fever with urinary symptoms
• Strep throat: High fever with severe sore throat
• Appendicitis: Fever with abdominal pain
• Meningitis: High fever with headache, stiff neck
• Sepsis: Life-threatening response to infection

Other Infections

• Malaria: Cyclic fevers with chills
• Tuberculosis: Low-grade, persistent fever
• Fungal infections: In immunocompromised individuals
• Parasitic infections: Various presentations

Non-Infectious Causes

• Inflammatory conditions: Rheumatoid arthritis, lupus
• Cancer: Lymphomas, leukemias, solid tumors
• Medications: Drug reactions or "drug fever"
• Blood clots: Deep vein thrombosis, pulmonary embolism
• Heat exhaustion: Overheating from environment
• Inflammatory bowel disease: Crohn's disease, ulcerative colitis
• Thyroid storm: Severe hyperthyroidism

In Children

• Teething: Low-grade fever sometimes occurs
• Immunizations: Mild fever is common after vaccines
• Ear infections: Very common cause in children
• Roseola: High fever followed by rash
• Kawasaki disease: Prolonged fever with other symptoms

Fever rarely occurs alone. Common accompanying symptoms include:

• Chills and shivering: Body trying to raise temperature
• Sweating: Body trying to cool down
• Headache: Common with fever
• Muscle aches: Body aches and pains
• Fatigue: Weakness and tiredness
• Loss of appetite: Reduced desire to eat
• Dehydration: From sweating and reduced intake
• Irritability: Especially in children
• Confusion: With high fevers
• Increased heart rate: Heart beats faster with fever
• Rapid breathing: Respiratory rate increases
• Delirium: In severe cases

General Measures

• Rest: Allow body to fight infection
• Hydration: Drink plenty of fluids
• Light clothing: Don't bundle up excessively
• Cool environment: Keep room comfortable
• Lukewarm bath: Can help reduce temperature
• Monitor temperature: Track fever pattern

Medications

Over-the-Counter Options

• Acetaminophen (Tylenol): Safe for most people
• Ibuprofen (Advil, Motrin): Also reduces inflammation
• Aspirin: For adults only (not children)
• Follow dosage instructions carefully
• Don't exceed maximum daily dose

Important Medication Notes

• Never give aspirin to children (Reye's syndrome risk)
• Alternate acetaminophen and ibuprofen if needed
• Don't wake sleeping child to give medicine
• Some people shouldn't take NSAIDs - check with doctor

When NOT to Treat Fever

• Low-grade fever in otherwise healthy person
• If person is comfortable despite fever
• Fever may help fight infection
• Focus on comfort, not number

Adults Should Seek Care For:

• Fever above 103°F (39.4°C)
• Fever lasting more than 3 days
• Fever with serious symptoms
• Fever that returns after going away
• No improvement with treatment
• Chronic medical conditions
• Recent surgery or hospitalization
• New medications started

Children Need Medical Care For:

• Any fever in infant under 3 months
• Fever above 104°F in any child
• Fever with lethargy or irritability
• Fever with rash
• Difficulty breathing
• Not drinking fluids
• Fever lasting more than 24 hours (under 2 years)
• Fever lasting more than 3 days (older children)

• Hand hygiene: Wash hands frequently and properly
• Vaccinations: Stay up-to-date with immunizations
• Avoid sick people: Limit exposure when possible
• Don't share items: Utensils, cups, towels
• Cover coughs: Use elbow or tissue
• Clean surfaces: Disinfect frequently touched areas
• Healthy lifestyle: Good nutrition, sleep, exercise
• Manage stress: Stress weakens immunity
• Stay home when sick: Prevent spread to others

Dehydration

• Common with fever
• Increased fluid needs
• Watch for dry mouth, decreased urination
• Can become serious quickly

Febrile Seizures

• Occur in some children
• Usually not harmful
• Scary but brief
• Call doctor after first occurrence

Hallucinations

• Can occur with high fever
• More common in children
• Usually resolve with fever reduction
• Monitor closely