Fever

Fever is your body's natural response to infection or illness, raising body temperature to help fight germs. It may feel uncomfortable but often signals your immune system is at work.

Medical illustration about Fever

Possible Causes

Fever in Adults

  • Viral infections like flu or COVID-19 — Research suggests viruses may trigger fever as the body ramps up its defense, common in otherwise healthy adults (Mayo Clinic).
  • Bacterial infections such as urinary tract infections (UTIs) or pneumonia — Bacteria might cause fever in adults, especially if the infection spreads or weakens immunity (CDC).
  • Medications or vaccines — Some drugs or shots could lead to temporary fever as a side effect in adults (NIH).
  • Autoimmune conditions like rheumatoid arthritis — Inflammation from these disorders may raise body temperature in some adults (Mayo Clinic).
  • Cancers such as lymphoma — Certain tumors might cause persistent fever in adults, though this is less common (NIH).

Fever in Children

  • Viral illnesses like roseola or common cold — Viruses often lead to fever in children as their immune systems respond strongly (AAP via Mayo Clinic).
  • Ear infections or strep throat — Bacterial causes may spark fever, especially in young kids prone to these (CDC).
  • Vaccinations — Mild fever might follow shots as the body builds immunity (NIH).
  • Gastroenteritis (stomach bugs) — Infections from viruses or bacteria could cause fever along with tummy troubles in children (Mayo Clinic).

Fever in Elderly

  • Urinary tract infections (UTIs) — UTIs may cause fever in older adults, sometimes without typical burning pain due to milder symptoms (NIH).
  • Pneumonia — Lung infections might trigger fever, but elderly people could have lower fevers despite serious illness (CDC).
  • Weakened immune system from age or conditions — Age-related changes may make infections like flu cause fever more easily (Mayo Clinic).
  • Medications — Polypharmacy in seniors could lead to drug-induced fevers in some cases (NIH).
  • Underlying chronic diseases like diabetes — Conditions that impair immunity might result in fever from minor infections (CDC).

Fever in Pregnant Women

  • Viral infections such as flu or COVID-19 — Pregnancy may heighten fever risk from viruses due to immune changes (CDC).
  • Urinary tract infections (UTIs) — UTIs are common in pregnancy and might cause fever if untreated (Mayo Clinic).
  • Listeria or other foodborne illnesses — Bacterial infections from food could lead to fever, posing risks to baby (CDC).
  • Pyelonephritis (kidney infection) — Upper UTIs may cause high fevers in pregnant women (NIH).

When to See a Doctor

Talk to your doctor right away if a baby under 3 months has any fever over 100.4°F (38°C) rectally, as it could signal a serious infection. For kids 3-6 months, seek care for fevers above 102°F (38.9°C) or if they seem very fussy, sleepy, or not drinking well. Children over 6 months with fevers lasting over 24 hours, or any child with breathing trouble, stiff neck, rash, or seizures need prompt medical help (Mayo Clinic, CDC).

In adults, consult a healthcare professional for fevers over 103°F (39.4°C), those lasting more than 3 days, or with severe headache, chest pain, confusion, or trouble breathing. Elderly folks might not spike high fevers, so any new fever or worsening symptoms warrants a check, as infections can progress quickly. Pregnant women should see a doctor for any fever, especially over 100.4°F (38°C), to protect both mom and baby (NIH).

Always seek emergency care for seizures, extreme lethargy, or dehydration signs like dry mouth or no tears. These red flags might point to something serious, so don't wait—call your provider or go to urgent care.

Home Remedies

Rest and stay hydrated with plenty of fluids like water or electrolyte drinks, as fever might cause dehydration. Dress in light clothing and keep the room cool to help comfort, but avoid ice baths which could cause chills (Mayo Clinic).

Over-the-counter meds like acetaminophen or ibuprofen may lower fever and ease aches in some cases, but follow dosing carefully by age and weight—never give aspirin to kids due to Reye's syndrome risk. Lukewarm sponge baths might soothe, but research suggests they're not always needed (CDC).

These steps may help mild fevers, but they're not a cure. Consult a healthcare professional if fever persists over 3 days, worsens, or you have concerns—always talk to your doctor before starting remedies, especially for kids, elderly, or pregnant women.

Frequently Asked Questions

What counts as a fever?

A fever may be a rectal temperature over 100.4°F (38°C) in infants or 100.4°F+ orally in adults, though normal varies by time of day and person. Use reliable thermometers like rectal for babies or oral for adults (Mayo Clinic).

Is a fever harmful?

Fevers under 104°F (40°C) are often not dangerous and might help fight infection, per research. High or prolonged fevers could be risky, especially in young kids or those with health issues—talk to your doctor (NIH).

How do I measure temperature accurately?

Rectal is best for infants; oral or ear for older kids and adults. Forehead scanners may be less precise. Clean the thermometer and note the method when sharing with your provider (CDC).

Can teething cause fever in babies?

Teething might cause slight temp rises, but true fevers over 100.4°F (38°C) are unlikely from it alone. Check for other signs of illness and consult a pediatrician (AAP via Mayo Clinic).

Should I treat every fever?

Treatment isn't always needed if the person feels okay—focus on comfort. Meds may help discomfort, but fever itself often resolves. Always ask your healthcare provider for advice tailored to you (NIH).

What about fever in pregnancy?

Any fever in pregnancy warrants a doctor's visit, as it might harm the baby. Stay hydrated and rest, but seek care promptly to rule out infections (CDC).

Sources

  1. Fever - Symptoms & causes. Mayo Clinic
  2. Fever. NIH / MedlinePlus
  3. Fever (Hyperthermia). CDC
  4. Fever in Children. American Academy of Pediatrics
  5. Fever. WHO