Fever

DEFINITION

• Rectal, Ear or Temporal Artery (TA) temperature: 100.4° F (38.0° C) or higher
• Pacifier or Oral temperature:  100° F (37.8° C) or higher
• Axillary (armpit) temperature:  99° F (37.2° C) or higher
• Limitation: Ear (Tympanic Membrane) temperatures are not reliable before 6 months of age
• Temporal artery and skin infrared temperatures may be reliable in young infants (new research)
• Use this guideline if fever is your child's only symptom

Causes

• Main cause: colds and other viral infections
• Fever may be the only symptom for the first 24 hours (i.e., viral fevers). The onset of symptoms (runny nose, cough, diarrhea, etc.) are often delayed. In the case of Roseola, fever may be the only symptom for 2 or 3 days.
• The cause of the fever usually can't be determined until other symptoms develop. That may take 24 hours.
• Bacterial infections (e.g.,  Strep throat or urinary tract infections) also cause fever
• Teething does not cause fever

Normal Variation of Temperature

• Rectal: A reading of 98.6° F (37° C) is just the average rectal temperature. It normally can change from 96.8° F (36° C) in the morning to a high of 100.3° F (37.9° C) in the late afternoon.
• Oral: A reading of 97.6° F (36.5° C) is just the average oral temperature. It normally can change from a low of 95.8° F (35.5° C) in the morning to a high of 99.4° F (37.5° C) in the late afternoon.

Return to School

• Your child can return to day care or school after the fever is gone and your child feels well enough to participate in normal activities.

See More Appropriate Topic (instead of this one) If

• Other symptom is present with the fever, see that topic (e.g., Colds, Cough, Sore Throat, Earache, Sinus Pain, Diarrhea, Vomiting, Rash - Widespread and Cause Unknown).
• Fever onset within 24 hours of receiving vaccine, see Immunization Reactions
• Fever onset 6-12 days after measles vaccine OR 17-28 days after chickenpox vaccine, see Immunization Reactions

When to Call Your Doctor

Home Care Advice for Fever

1. Reassurance: Presence of a fever means your child has an infection, usually caused by a virus. Most fevers are good for sick children and help the body fight infection.  Use the following definitions to help put your child's level of fever into perspective:
   • 100°-102°F (37.8° - 39°C) Low grade fevers: beneficial, desirable range
   • 102°-104°F (39 - 40°C)     Mild fever: still beneficial
   • Over 104°F (40°C)          Moderate fever: causes discomfort, but harmless
   • Over 105°F (40.6°C)       High fever: higher risk of bacterial infections
   • Over 106°F (41.1°C)       Very high fever: important to bring it down
   • Over 108°F (42.3°C)       Dangerous fever: fever itself can harm brain
2. Treatment for All Fevers:  Extra Fluids and Less Clothing
   • Give cold fluids orally in unlimited amounts (reason: good hydration replaces sweat and improves heat loss via skin).
   • Dress in 1 layer of light weight clothing and sleep with 1 light blanket (avoid bundling).  (Caution: overheated infants can't undress themselves.)
   • For fevers 100°-102° F (37.8° - 39°C), this is the only treatment needed (fever medicines are unnecessary).
3. Fever Medication:  
   • Fevers only need to be treated with medicine if they cause discomfort. That usually means fevers above 102°F (39°C).
   • Give acetaminophen (e.g., Tylenol) or ibuprofen (e.g., Advil). See the dosage charts.
   • The goal of fever therapy is to bring the temperature down to a comfortable level. Remember, the fever medicine usually lowers the fever by 2° to 3° F (1 - 1.5° C).
   • Avoid aspirin (Reason: risk of Reye's syndrome, a rare but serious brain disease)
   • Avoid alternating acetaminophen and ibuprofen (Reason: unnecessary and risk of overdosage)
4. Sponging:
   • Note: Sponging is optional for high fevers, not required.
   • Indication: May sponge for (1) fever above 104° F (40° C) AND (2) doesn't come down with acetaminophen (e.g., Tylenol) or ibuprofen (always give fever medicine first).
   • How to sponge: Use lukewarm water (85 - 90° F) (29.4 - 32.2° C). Do not use rubbing alcohol. Sponge for 20-30 minutes.
   • If your child shivers or becomes cold, stop sponging or increase the water temperature.
5. Contagiousness:  Your child can return to day care or school after the fever is gone and your child feels well enough to participate in normal activities.
6. Expected Course of Fever:  Most fevers associated with viral illnesses fluctuate between 101° and 104° F (38.4° and 40° C) and last for 2 or 3 days.
7. Call Your Doctor If:
   • Fever goes above 104° F (40° C) repeatedly
   • Any fever occurs if under 12 weeks old
   • Fever without a cause persists over 24 hours (if age less than 2 years)
   • Fever persists over 3 days (72 hours)
   • Your child becomes worse

And remember, contact your doctor if your child develops any of the "Call Your Doctor" symptoms.

Disclaimer: This information is not intended be a substitute for professional medical advice. It is provided for educational purposes only. You assume full responsibility for how you choose to use this information.

Author and Senior Reviewer: Barton D. Schmitt, M.D.

Last Reviewed: 1/4/2010

Last Revised: 12/11/2009

Content Set: Pediatric HouseCalls Symptom Checker

Copyright 1994-2010 Barton D. Schmitt, M.D.