• An abnormal high body temperature
  • Fever is the only symptom. Your child has a true fever if:
  • Rectal (Bottom), Ear or Forehead temperature: 100.4° F (38.0° C) or higher
  • Oral (Mouth) temperature: 100° F (37.8° C) or higher
  • Under the arm (Armpit) temperature: 99° F (37.2° C) or higher
  • Caution: ear temperatures are not accurate before 6 months of age
  • Caution: forehead temperatures must be digital. Forehead strips are not accurate.

Causes of Fever

  • Overview. Almost all fevers are caused by a new infection. Viruses cause 10 times more infections than bacteria. The number of germs that cause an infection are in the hundreds. Only a few common ones will be listed.
  • Viral Infections. Colds, flu and other viral infections are the most common cause. Fever may be the only symptom for the first 24 hours. The start of viral symptoms (runny nose, cough, loose stools) is often delayed. Roseola is the most extreme example. Fever may be the only symptom for 3 to 5 days. Then a rash appears.
  • Bacterial Infections. A bladder infection is the most common cause of silent fever in girls.
  • Sinus Infection. This is a problem caused by a cold. The main symptom is the return of fever after it has been gone for a few days. The sinus congestion also changes to sinus pain. Color of nasal discharge is not very helpful for making this diagnosis.
  • Vaccine Fever. Fever with most vaccines begins within 12 hours. It lasts 2 to 3 days. This is normal and harmless. It means the vaccine is working.
  • Newborn Fever (Serious). Fever that occurs during the first 3 months of life can be serious. All of these babies need to be seen as soon as possible. The fever may be due to sepsis (a bloodstream infection). Bacterial infections in this age group can get worse quickly. They need rapid treatment.
  • Meningitis (Very Serious). A bacterial infection of the membrane that covers the spinal cord and brain. The main symptoms are a stiff neck, headache and confusion. Younger children are lethargic or so irritable that they can't be consoled. If not treated early, can suffer brain damage.
  • Normal Overheating. The fever is usually low grade. Can occur during heat waves or from being overdressed. The temp becomes normal in a few hours after moving to a cooler place. Can also occur during hard exercise. Fever goes away quickly with rest and drinking extra fluids.
  • Not Due to Teething. Research shows that "getting teeth" does not cause fevers.

Fever and Crying

  • Fever on its own shouldn't cause much crying.
  • Frequent crying in a child with fever is caused by pain until proven otherwise.
  • Hidden causes can be ear infections, kidney infections, sore throats and meningitis.

Roseola: Classic Cause of Unexplained Fever in Young Children

  • Most children get Roseola between 6 months and 3 years of age.
  • Cause: human herpes virus 6
  • Rash: pink, small, flat spots on the chest and stomach. Rash is the same on both sides of the body.
  • Then spreads to the face.
  • Classic feature: 2 or 3 days of high fever without a rash or other symptoms.
  • The rash starts 12 to 24 hours after the fever goes away.
  • The rash lasts 1 to 3 days.
  • By the time the rash appears, the child feels fine.

Normal Temperature Range

  • Rectal. A reading of 98.6° F (37° C) is just the average rectal temp. A normal low can be 96.8° F (36° C) in the morning. It can change to a high of 100.3° F (37.9° C) late in the day. This is a normal range.
  • By mouth. A reading of 97.6° F (36.5° C) is just the average mouth temp. A normal low can be 95.8° F (35.5° C) in the morning. It can change to a high of 99.9° F (37.7° C) late in the day. This is a normal range.

When To Call

Call 911 Now

  • Not moving or too weak to stand
  • Can't wake up
  • Severe trouble breathing (struggling for each breath; can barely speak or cry)
  • Purple or blood-colored spots or dots on skin
  • You think your child has a life-threatening emergency

Go to ER Now

  • Stiff neck (can't move neck normally)
  • Age less than 1 year and soft spot bulging or swollen
  • Hard to wake up
  • Had a seizure with the fever
  • Not alert when awake ("out of it")
  • Acts or talks confused

Call Doctor or Seek Care Now

  • Trouble breathing, but not severe
  • Great trouble swallowing fluids or spit
  • Fever in baby less than 12 weeks old. Caution: do NOT give your baby any fever medicine before being seen.
  • Fever higher than 104° F (40° C)
  • Shaking chills (shivering) lasting more than 30 minutes
  • Nonstop crying or cries when touched or moved
  • Won't move an arm or leg normally
  • Dehydration suspected. No urine in more than 8 hours, dark urine, very dry mouth and no tears.
  • Pain or burning when passing urine
  • Weak immune system. Examples are: sickle cell disease, HIV, cancer, organ transplant, taking oral steroids.
  • Your child looks or acts very sick
  • You think your child needs to be seen, and the problem is urgent

Contact Doctor Within 24 Hours

  • Age 3-6 months old with fever
  • Age 6-24 months old with fever that lasts more than 48 hours. There are no other symptoms (such as cough or diarrhea).
  • Fever lasts more than 3 days
  • Fever returns after being gone more than 24 hours
  • Recent travel outside the country to high risk area
  • You think your child needs to be seen, but the problem is not urgent

Contact Doctor During Office Hours

  • You have other questions or concerns

Self Care at Home

  • Fever with no other symptoms and your child acts mildly ill

Care Advice

What You Should Know About Fever:

  • Having a fever means your child has a new infection.
  • It's most likely caused by a virus.
  • You may not know the cause of the fever until other symptoms develop. This may take 24 hours.
  • Most fevers are good for sick children. They help the body fight infection.
  • Use the ranges below to help put your child's level of fever into perspective:
    • 100° - 102° F (37.8° - 39° C) Low grade fever: helpful, good range. Don't treat.
    • 102° - 104° F (39 - 40° C) Average fever: helpful. Treat if causes discomfort.
    • Higher than 104° F (40° C) High fever: causes discomfort, but harmless. Always treat.
    • Higher than 106° F (41.1° C) Very high fever: important to bring it down. Rare to go this high.
    • Higher than 108° F (42.3° C) Dangerous fever: fever itself can be harmful.

Treatment for All Fevers - Extra Fluids

  • Fluids alone can lower the fever. Reason: being well-hydrated helps the body give off heat through the skin.
  • Offer your child extra water or other fluids by mouth. Cold fluids are better. Until 6 months old, only give extra formula or breastmilk.
  • For all children, dress in 1 layer of light weight clothing, unless shivering. Reason: also helps heat loss from the skin.
  • For shivering (or the chills), give your child a blanket. Make them comfortable.
  • Caution: if a baby under 1 year has a fever, never overdress or bundle up. Reason: babies can get over-heated more easily than older children.

Fever Medicine:

  • For fevers 100°- 102° F (37.8° - 39°C), fever meds are not needed. Reason: fevers in this range help the body fight the infection. Fevers turn on the body's immune system. Fevers do not cause any discomfort.
  • Fever meds are mainly needed for fevers higher than 102° F (39° C).
  • Give an acetaminophen product (such as Tylenol).
  • Another choice is an ibuprofen product (such as Advil).
  • Goal of treatment: keep the fever at a helpful level. Most often, the fever meds lower the fever by 2° to 3° F (1 - 1.5° C). They do not bring it down to normal. It takes 1 or 2 hours to see the effect.
  • Do not use aspirin. Reason: risk of Reye syndrome, a rare but serious brain disease.
  • Do not use both acetaminophen and ibuprofen together. Reason: not needed and a risk of giving too much.
  • Pain: fever does not cause pain. If your child also has pain, it's from the infection. It may be a sore throat or muscle pain. Treat the pain, if it's more than mild.

Sponging with Lukewarm Water:

  • Note: sponging is an option for high fevers, but not required. It is rarely needed.
  • When to Use: fevers higher than 104° F (40° C) AND doesn't come down with fever meds. Always give the fever medicine at least an hour to work before sponging.
  • How to Sponge: use lukewarm water (85 - 90° F) (29.4 - 32.2° C). Sponge for 20-30 minutes.
  • If your child shivers or becomes cold, stop sponging. Other option: you can also make the water warmer.
  • Caution: do not use rubbing alcohol. Reason: can cause a coma.

Return to School:

  • Your child can return to school after the fever is gone. Your child should feel well enough to join in normal activities.

What to Expect:

  • Most fevers with viral illnesses range between 101° and 104° F (38.4° and 40° C).
  • They may last for 2 or 3 days.
  • They are not harmful.

Call Your Doctor If:

  • Your child looks or acts very sick
  • Any serious symptoms occur such as trouble breathing
  • Fever goes higher than 104° F (40° C)
  • Any fever occurs if less than 12 weeks old
  • Fever without other symptoms lasts more than 48 hours if age less than 2 years
  • Fever lasts more than 3 days (72 hours)
  • You think your child needs to be seen
  • Your child becomes worse


Barton Schmitt MD, FAAP
Disclaimer: this health information is for educational purposes only. You, the reader, assume full responsibility for how you choose to use it.
select new symptom