Merck Manual

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Quick Facts

Febrile Seizures


The Manual's Editorial Staff

Last full review/revision May 2020| Content last modified May 2020
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What are febrile seizures?

Febrile means having a fever. Seizures are convulsions (sudden, jerking motions) caused by an abnormal burst of electrical activity in the brain. Febrile seizures are convulsions that children sometimes get because of a fever. The seizures:

  • Are triggered by a high fever

  • Most often occur in otherwise healthy children, ages 6 months to 3 years

  • Last less than 15 minutes

  • Usually run in families

Many children who have a febrile seizure only ever have one.

Although febrile seizures can be scary to watch, they're harmless. However, some serious disorders such as brain infections (meningitis) cause both fever and seizures. In those cases, it's the serious disorder that causes the seizure, not the fever itself. Seizures caused by a serious disorder aren't considered a febrile seizure.

What causes febrile seizures?

Febrile seizures are triggered by a fever. The fever is often caused by a mild infection, like a cold or an ear infection. No one knows why a fever sometimes causes seizures in a child.

What are the symptoms of febrile seizures?

There are two types of febrile seizures—simple and complex. They have different symptoms.


  • Your child's entire body shakes for less than 15 minutes


  • Your child's entire body shakes for more than 15 minutes (constantly or with pauses), or

  • Only one side of your child's body shakes, or

  • Seizures occur at least twice within 24 hours

During the seizure, your child won't be aware of you or be able to talk. However, your child will keep breathing.

What tests will the doctor do?

Because some serious brain infections that cause fevers also cause seizures, a doctor needs to check your child. Take your child to the emergency room if your child has a seizure and your child:

  • Has a fever, or

  • Never had a seizure before, or

  • Is very sick

Doctors will ask about your child's symptoms and then examine your child.

Depending on what they find, doctors may order tests to look for other serious disorders. Your child may need:

  • A spinal tap to check for a brain infection (the doctor inserts a needle into your child’s lower back to take a sample of the fluid that is around the brain and spinal cord)

  • An MRI (a scan showing detailed pictures)

  • Blood tests

Most children won't need these additional tests. Most children will only ever have one febrile seizure.

How do doctors treat febrile seizures?

For seizures lasting less than 15 minutes:

  • Medicine to decrease your child’s fever

  • Usually no other treatment

For seizures lasting 15 minutes or more:

  • Medicines to stop seizures (anticonvulsants)

Most children won't have to take medicine every day to prevent seizures. Doctors only give medicine to prevent seizures to children who've had:

  • Many febrile seizures

  • Seizures lasting a long time

Will my child have more seizures?

If your child has one or two simple febrile seizures, your child is only slightly more likely than other children to have a seizure disorder (seizures without fever). If your child has complex febrile seizures or has other medical problems, your child has a higher risk of developing a seizure disorder.

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
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