It depends on how you are using the term. The terms febrilemeans to have a fever or to be excited.There is also a febrile seizure, and that is a type of seizurewhere the person's body temperature rises. It seems that upperrespiratory infections or viruses precipitate those. So you wouldhave to be sick or recovering from a recent illness to have thistype of seizure. If you mean age, then you'd most likely be fromsix months to age six, and boys are twice as likely to suffer thisthan girls.