- 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 2 or 3 days. Then a rash appears.
- Bacterial Infections. A bladder infection is the most common cause of silent fever in girls. Strep throat is also a common cause of unexplained fever.
- 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.
- Overheated. 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.