A fever is an increase in the body's temperature. The best way to measure a small child’s temperature is using a rectal thermometer. A rectal temperature of 100.4 degrees F or higher is considered a fever. For oral thermometers, 99.5 degrees F or higher is considered a fever; for under-the-arm thermometers, it is 99.0 degrees F. For ear thermometers it is 100.4 degrees F, but they are not as reliable in children under six months of age.
Function
According to the Merck Manuals, fevers help protect the child from infection and injury. The elevated temperature is a response to pyrogens, substances produced by both invading microbes and the body’s own immune system cells. Pyrogens travel to the hypothalamus, the body’s thermostat in the brain, triggering a reaction that raises the body’s baseline temperature. The high temperature disrupts the microbe’s ability to reproduce, helping control the infection.
Significance
Small children have a relatively weak immune system, in part because they have not been exposed to many microbes that would help build up their immunity to infection. This puts them at risk for the development of serious bacterial infections, such as urinary tract infections, pneumonia, bacteremia, which is the presence of bacteria in the blood stream, meningitis, which is inflammation of the meninges, the tissue covering the brain and the spinal cord, and colitis, which is inflammation of the large intestine. This is especially true in infants up to three months of age.
Other Symptoms
Small children can have other symptoms associated with the fever. According to the Mayo Clinic, these include sweating, shivering, weakness, headache, loss of appetite, dehydration and changes in mental status, with confusion and hallucinations.
Misconceptions
Many myths surround fevers in small children, for example that fevers cause sterility or that they cause brain damage. Seizures can result from fevers, but the so-called febrile seizures occur with a rapid rise in the child’s temperature, not necessarily that it reaches a high number. And brain damage can occur if the child suffers from hyperpyrexia, a dangerous but rare condition in which the brain’s thermostat, the hypothalamus, malfunctions, and the body’s temperature reaches 106 degrees or above.
Warning
The Mayo Clinic recommends that caregivers call the doctor if a child has a fever without an obvious source, if the fever is higher than 103 degrees F--or 101 degrees F for an infant, if the child is irritable and inconsolable, if he is dehydrated or is vomiting and taking oral liquids appropriately, or if the child is unresponsive or lethargic.
