The usual seizure lasts three to five minutes and is harmless to the child.
Febrile seizures are essentially impossible to prevent.
They generally occur on a rapid upswing in the temperature, often before the parents are aware the child even has a fever. Most children only have one or at most two such seizures in childhood. They do not cause epilepsy later in life. Febrile seizures are limited to the young, probably under three years old. A seizure with a concomitant fever in an older child is a different animal and may indeed be related to epilepsy.