Many parents fear that fevers will cause brain damage. Brain damage from a fever will not occur unless the fever is over 107.6 degrees F (42C) for an extended period of time. Many also fear that untreated fevers will keep going higher and higher, up to 107 degrees F or even more. Untreated fevers caused by infection will seldom go over 105 degrees unless the child is overdressed, or trapped in a hot place. The brain's thermostat will stop the fever from climbing above 106 degrees F.

Some parents fear that fevers will cause seizures. For the great majority of children this is not the case. About 4% of children, though, will sometimes have seizures with fever. These febrile seizures are caused by rapid increase in temperature, not by the height of the temperature. Once a child already has a high fever, a febrile seizure is unlikely with the current illness. In any event, febrile seizures are over in moments with no lasting consequences. Treating fevers early in these children may prevent further febrile seizures.