A febrile seizure is a convulsion associated with a fever in infants or small children. A febrile seizure is diagnosed when all underlying causes are eliminated, such as meningitis , encephalitis , or any other intracranial disease.

There are two types of febrile seizures:

  • Simple febrile seizures—convulsions last between a few seconds to 15 minutes and are followed by a period of confusion and sleepiness which slowly resolves
  • Complex febrile seizures—last longer than 15 minutes, occur more than once within 24 hours, or produce convulsions which affect only part the body


Elevated body temperature associated with a fever is believed to trigger the seizure. The common causes of fever include any childhood infection, especially viral infections. Fever associated with routine immunizations may also cause a febrile seizure.

Risk Factors

Age is the greatest risk factor. Two to four percent of children have a febrile seizure before age five. There is some evidence that seizures associated with a high fever can occur if there is a family history of them.


Signs of a febrile seizure include:

  • A fever, usually above 102°F
  • Convulsion (jerking or stiffening muscles)
  • Abnormal eye movements
  • Coarse breathing sounds during the convulsion
  • Loss of consciousness
  • Loss of bladder or bowel control
  • Vomiting
  • Brief period of drowsiness or confusion following a seizure

A typical seizure produces generalized shaking, twitching, or muscle rigidity. It is usually associated with loss of consciousness. The seizure typically lasts anywhere from a few seconds to a few minutes.

Febrile seizures occur between the ages of three months to five years, with the usual age being 6 months to 3 years. About 30% of children suffer recurrent simple febrile seizures. Of those children, 50% of the seizures usually occur in the first year, and 90% occur within 2 years.

In general, the younger the age that the first febrile seizure occurs, the more likely it is that a child will have another seizure.

The long-term risk of developing adult epilepsy is very low (less than 1% for a child with a simple febrile seizure). This risk is higher for children with:

  • A complex febrile seizure
  • Problems in development before the febrile seizure
  • A family history of a seizure disorder

The long-term risk of developing physical or mental problems is also very low.

If you suspect your child is having a febrile seizure, act quickly:

  • Protect from physical injury—Place your child on the floor or bed away from any hard or sharp objects.
  • Protect airway—Do not place anything in the mouth during the convulsion. Turn the child’s head to the side to allow saliva or vomit to drain from the mouth.
  • Watch the time—The length of the convulsions should be less than five minutes. Unless the doctor has told you otherwise, call 911.


In the case of simple febrile seizures, the diagnosis revolves around determining the source of the fever. This may require blood or urine tests. Rarely, if the doctor suspects meningitis or encephalitis , a lumbar puncture may be needed to analyze the spinal fluid.

In the case of complex febrile seizures, the source of the fever is important. Additional neurologic evaluation may be needed, including:

  • CT scan —a type of x-ray that uses a computer to make pictures of structures inside the head
  • MRI scan —a test that uses magnetic waves to make pictures of structures inside the head
  • Electroencephalogram (EEG)—a test used to evaluate brain function or disorders

MRI Scan

MRI of the Brain
© 2009 Nucleus Medical Art, Inc.


In most cases, the seizure resolves within a few minutes. Treatments are targeted at determining the underlying source of fever, which may require antibiotics or antiviral medications. In the rare case of a persistent seizure, call 911 and give antiseizure medication if necessary.

If your child is diagnosed as having febrile seizures, follow your doctor's instructions.


About 30% of children will suffer another febrile seizure when they have a fever. This tendency is outgrown, and very few will develop epilepsy . Giving your child acetaminophen at the first sign of a fever may help prevent recurrent febrile seizures. Unfortunately, a fever can happen suddenly, with the seizure being the first sign. Do not give oral medications during a seizure.

Do not give aspirin to children or teens who have a current or recent viral infection. This is because of the risk of Reye's syndrome .

Daily antiseizure medications, such as phenobarbital and valproic acid , can be used to prevent seizures. These medications do have side effects, though. Simple febrile seizures, while alarming, do not harm the brain.

Given the side effects, medications are not routinely recommended. In children with recurrent febrile seizures, your doctor may prescribe rectal valium to stop the seizure if it lasts more than 4-5 minutes.