If you’re wondering why your child had a febrile seizure, the most common cause is a fever linked to an illness. This page explains what triggers febrile seizures, whether a high fever or a fast-rising fever may play a role, and which risk factors can make them more likely.
Share what happened around your child’s fever to get personalized guidance on common febrile seizure causes in toddlers and children, including illness, rapid temperature rise, vaccines, and other risk factors.
Febrile seizures happen when a child’s developing brain reacts to a fever, usually during a common illness such as a viral infection, cold, flu, ear infection, or other fever-causing illness. In many cases, it is not the exact temperature alone that matters. A seizure can happen early in an illness, sometimes when the fever is rising quickly, and sometimes before a parent even realizes the child is sick. This is why a fever can cause a seizure in a child even when the fever does not seem extremely high.
The most common cause of febrile seizure during illness is a fever from a viral or bacterial infection. Many children have febrile seizures with routine childhood illnesses.
What triggers febrile seizures is often the speed of the temperature change rather than the highest number on the thermometer. A rapid rise can be enough to trigger one.
Some children develop a fever after certain vaccines, and that fever can rarely be linked to a febrile seizure. This does not mean the vaccine directly caused epilepsy or a long-term seizure disorder.
A very high fever can be involved, but many febrile seizures happen before the fever peaks. Parents often ask why did my child have a febrile seizure when the temperature did not seem severe yet.
A seizure may happen at the start of an illness, when the body temperature is climbing. This helps explain why febrile seizure causes in toddlers are not always obvious in the moment.
Some children are more sensitive to fever than others. Two children can have the same illness and temperature, but only one may have a febrile seizure.
Febrile seizures are most common between about 6 months and 5 years of age, with toddlers especially affected because their brains are still developing.
What makes a child have a febrile seizure can include genetics. A family history of febrile seizures can increase the chance that a child will have one.
Illnesses that cause fever, especially viral infections, are a major trigger. The cause of febrile seizure during illness is usually the fever response, not the seizure itself causing the fever.
If you are trying to understand what causes febrile seizures in children, it can help to look at the full picture: what illness was present, how quickly the fever started, whether there was a recent vaccine, your child’s age, and any family history. While febrile seizures are frightening to witness, they are often linked to common childhood fevers rather than a serious brain condition. Personalized guidance can help you sort through the most likely cause and what to discuss with your child’s clinician.
Yes. A febrile seizure can happen when a fever is rising quickly, even before it reaches a very high number. That is one reason parents may be surprised when a seizure happens early in an illness.
Toddlers are in the age range when febrile seizures are most common because their brains are still developing and may be more sensitive to fever. Age is one of the main risk factors.
The most likely cause is the fever response itself, often from a viral infection or other routine childhood illness. In many cases, the trigger is the fever starting or rising quickly rather than the illness being unusually severe.
Not always. A high fever can be part of the picture, but many febrile seizures are linked to how fast the temperature changes. Some children have them with moderate fevers, while others never do even with higher temperatures.
A vaccine can sometimes lead to a fever, and that fever can rarely trigger a febrile seizure in a child who is susceptible. This is different from a vaccine directly causing a chronic seizure disorder.
Answer a few questions about the fever, illness timing, and possible risk factors to better understand the likely cause and what steps may help you feel more prepared next time.
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Febrile Seizures
Febrile Seizures
Febrile Seizures
Febrile Seizures