If your child ever had a febrile (fever) seizure, it’s something you probably won’t forget. But while these fits and spasms look scary, usually there are no long-term effects.
Doctors aren’t certain about how it’s triggered. A temperature above 100.4 F may do it, or the seizure may be a result of how quickly your child’s fever spikes. You’re likely to notice the seizure, then feel that she’s burning up. It may be the first indication you have of her being sick.
Who gets a Febrile Seizure?

Kids between 3 months and 6 years of age can get one. But they’re most common in toddlers-between 12 and 18 months. Children usually outgrow them by the time they’re 6 years old.
Your child is more likely to get one if other people in your family have had one. A second seizure also is more likely once your child has had the first one.
What does it look like?
That depends on the type of febrile seizure.
Simple seizures: These are the most common and usually are over in a minute or two. But they can last as long as 15 minutes.
Symptoms include:
  • Convulsions – shaking and twitching all over the body
  • Eye-rolling
  • Unresponsiveness
  • Moaning
  • Losing bowel or bladder control
  • Bleeding tongue or mouth from biting down
Your child may feel sleepy, irritable, cranky or confused for a few hours once it’s over.
Complex seizures: These are less common and can last longer than 15 minutes. Your child may have more than one in a day. Only one part of your child’s body may twitch or shake. Afterwards, her arm or leg may feel weak.
A complex febrile seizure is a greater concern. It may require additional diagnosis or hospital admission.
What causes them? 

Any time your child has a temperature and is under the age of 6, a febrile seizure is possible. These are the most common reasons for a fever:

Infections: If your child picked up a bacterial or viral infection she may get a temperature. Roseola, also known as sixth disease, is often a culprit because it causes a fever to spike quickly.
VaccinationsFevers may follow some immunizations -- especially the one for measlesmumps and rubella (MMR). Your child may get a temperature 8 to 14 days after the shot.