Child or adult? Causes of seizures in infants and children can include a high fever and a condition called pku (phenylketonuria). In adults, there are many possible causes including brain tumor, low blood sugar, head injury, some illegal drugs (pcp, cocaine, "speed"), stroke, toxemia of pregnancy, epilepsy, and many more. If someone has a seizure for the first time, a doctor needs to do tests to find out why.
Various. Untreated or poorly controlled epileptics can have increased seizures with infections, fevers, lack of sleep, poor dietary habits, alcohol ingestion, use of recreational drugs, rapid cessation of certain medications, contact with stimulants, undue stressors, etc. So, best to use medications and perhaps a vagal nerve stimulator to enhance control.