Febrile seizures affect 2% to 5% of children in the U.S. and Europe, making them the most common type of seizure in early childhood. They occur during fevers, typically between the ages of 6 months and 5 years, with the highest rate between 12 and 18 months of age. If your child has had one, or you’re wondering whether they will, here’s what the numbers actually look like.
How Common Is a First Febrile Seizure?
Roughly 1 in 20 to 1 in 50 children will have at least one febrile seizure before they turn 5. The peak window falls between 12 and 18 months, when the developing brain is most susceptible to the rapid temperature changes that come with common childhood illnesses. After age 5, febrile seizures become rare as the brain matures past this vulnerability.
Most febrile seizures are “simple,” meaning they last under 15 minutes, involve the whole body rather than just one side, and don’t repeat within the same 24-hour illness. A smaller portion are considered “complex,” lasting longer, affecting only one part of the body, or recurring during the same fever. The simple type is far more common and carries a lower risk of any long-term effects.
Recurrence After the First Seizure
About 1 in 4 children who have a first febrile seizure will have another one within the following year. A study of 140 children aged 9 months to 5 years found a recurrence rate of 25.7% during one year of follow-up. That means roughly 3 out of 4 children never have a second episode.
Several factors push that number higher or lower. Age matters: the younger your child is at the first seizure, the more febrile illnesses they still have ahead of them, and each fever is another opportunity for a seizure. Children who seize at relatively low fevers also tend to recur more often, likely because their threshold for a seizure is lower than average.
How Family History Changes the Odds
Genetics play a significant role in how often febrile seizures happen within a family. If a parent or sibling has had febrile seizures, a child’s two-year recurrence risk nearly doubles, jumping from about 27% to 52%. When half or more of a child’s first-degree relatives have a history of febrile seizures, the recurrence risk climbs to roughly 83%.
Interestingly, more distant relatives don’t move the needle much. Having grandparents, aunts, uncles, or cousins with a history of febrile seizures does not significantly increase a child’s chance of recurrence. The genetic link appears strongest within the immediate family.
What a Febrile Seizure Looks Like
A simple febrile seizure typically lasts between one and three minutes. The child may stiffen, shake rhythmically, roll their eyes back, or become unresponsive. It can happen at the very beginning of a fever, sometimes before parents even realize their child is sick. That’s one reason febrile seizures feel so alarming: they can be the first sign of illness rather than a complication that builds gradually.
After the seizure stops, children enter a recovery phase. During this time they may seem confused, drowsy, or irritable. This post-seizure state generally lasts 5 to 30 minutes, though some children are groggy for an hour or two. Mood and energy levels can be off for the rest of the day. A seizure lasting more than 5 minutes, or one that affects only one side of the body, warrants emergency medical attention.
Long-Term Risk of Epilepsy
Most children who have febrile seizures do not develop epilepsy. The overall risk of epilepsy following febrile seizures is estimated at about 3% by age 7, rising to around 5% to 7% with longer follow-up. For comparison, the baseline risk of epilepsy in all children is about 1.2%, so febrile seizures roughly double to quintuple that risk depending on the timeframe measured.
A prospective study of over 600 children in Vietnam found that 5.5% developed epilepsy over a median follow-up of two years. Complex febrile seizures, a family history of epilepsy (not just febrile seizures), and seizures that recur frequently carry a higher risk than a single, simple event. A child who has one brief febrile seizure with no other risk factors sits at the low end of that range.
What Happens at the Hospital
After a simple febrile seizure, most children need no imaging or invasive testing. Medical guidelines across multiple countries agree that routine brain scans and spinal taps are not necessary for a child who has a straightforward febrile seizure and returns to their normal baseline quickly. Imaging is typically reserved for children who don’t fully wake up within a reasonable time, who show weakness on one side of the body afterward, or who had a prolonged or focal seizure that raises concern about an underlying cause.
The focus of the visit is usually identifying what’s causing the fever, whether that’s an ear infection, a virus, or something else. Treating the underlying illness matters more than the seizure itself, which in most cases resolves on its own and doesn’t require anti-seizure medication going forward. Preventive anti-seizure drugs are rarely prescribed for simple febrile seizures because the side effects generally outweigh the benefits for a condition most children outgrow entirely by age 5 or 6.