A febrile convulsion is a fit or seizure caused by a fever. They are caused by a sudden change in your child's body temperature and are usually associated with a fever (a temperature above 38°C). A high temperature is a sign of infection somewhere in the body and is often caused by a virus or bacteria.reatment of a fever with paracetamol or ibuprofen does not prevent a febrile convulsion. However, if your child is very uncomfortable, you can follow the simple steps found on the Kids Health Info factsheet: Fever in children.