The direct cause of a febrile seizure is not known, however, several increased risk factors are suggested including;

  • Age (90% of reported febrile seizures occur before the age of 3)
  • Parent or sibling who had febrile seizures or epilepsy (i.e. Genetics)
  • Gender (i.e. boys are twice a likely as girls)
  • Viral infections (e.g. Chicken Pox / Varicella, Influenza, HHV-6)
  • Vaccinations (e.g. MMR/MMRV, Chicken Pox / Varicella, Influenza) – please report directly in the UK with the Yellow Card system or in the US with the VAERS system.
  • Periodic fever syndromes (e.g. PFAPA)
  • Vitamin (e.g. Iron or Zinc) deficiency
  • Developmental delay
  • Shorter breast-feeding duration
  • Maternal smoking or drinking during pregnancy
  • Decreased gestational age at birth
  • Decreased birth weight
  • Breech delivery
  • Day care attendance (i.e. increased risk of viral / bacterial infections)

What is universally agreed, however, is that a sudden rise in core temperature (rather than a fever that has been present for a prolonged length of time) can cause a febrile seizure.

Febrile seizures are believed to be due to an immature / hypersensitive hypothalamus in the brain. The hypothalamus is responsible for homeostatic core temperature regulation, (amongst other factors) and in younger children it is still a developing portion of the brain, meaning it is susceptible to hypersensitive reactions to slight raises in body temperature.

Studies in the US, South America, and Western Europe show that anywhere from 2% to 5% of all children experience a febrile seizure before the age of five (5).  However, the frequency of occurrence is 7% in Japan and as high as 14% in the Mariana Islands.

For further information on susceptibility, please see the additional page on Genetics.