Usually, a child having a febrile seizure shakes all over and loses consciousness. Sometimes, the child may get very stiff or twitch in just one area of the body.

A child having a febrile seizure may:

• Have a fever higher than 100.4 F (38.0 C)
• Lose consciousness
• Shake or jerk the arms and legs

Febrile seizures are classified as simple or complex:

• Simple febrile seizures. This most common type lasts from a few seconds to 15 minutes. Simple febrile seizures do not recur within a 24-hour period and are not specific to one part of the body.
• Complex febrile seizures. This type lasts longer than 15 minutes, occurs more than once within 24 hours or is confined to one side of your child's body.

Febrile seizures most often occur within 24 hours of the onset of a fever and can be the first sign that a child is ill.

See your child's doctor as soon as possible after your child's first febrile seizure, even if it lasts only a few seconds. Call an ambulance to take your child to the emergency room if the seizure lasts longer than five minutes or is accompanied by:

• Vomiting
• A stiff neck
• Breathing problems
• Extreme sleepiness

Usually, a higher than normal body temperature causes febrile seizures. Even a low-grade fever can trigger a febrile seizure.

Infection

The fevers that trigger febrile seizures are usually caused by a viral infection, and less commonly by a bacterial infection. The flu (influenza) virus and the virus that causes roseola, which often are accompanied by high fevers, appear to be most frequently associated with febrile seizures.

Post-vaccination seizures

The risk of febrile seizures may increase after some childhood vaccinations. These include the diphtheria, tetanus and pertussis vaccine and the measles-mumps-rubella vaccine. A child can develop a low-grade fever after a vaccination. The fever, not the vaccine, causes the seizure.

Factors that increase the risk of having a febrile seizure include:

• Young age. Most febrile seizures occur in children between 6 months and 5 years of age, with the greatest risk between 12 and 18 months of age.
• Family history. Some children inherit a family's tendency to have seizures with a fever. Additionally, researchers have linked several genes to a susceptibility to febrile seizures.

Most febrile seizures produce no lasting effects. Simple febrile seizures don't cause brain damage, intellectual disability or learning disabilities, and they don't mean your child has a more serious underlying disorder.

Febrile seizures are provoked seizures and don't indicate epilepsy. Epilepsy is a condition characterized by recurrent unprovoked seizures caused by abnormal electrical signals in the brain.

Recurrent febrile seizures

The most common complication is the possibility of more febrile seizures. The risk of recurrence is higher if:

• Your child's first seizure resulted from a low-grade fever.
• The febrile seizure was the first sign of illness.
• An immediate family member has a history of febrile seizures.
• Your child was younger than 18 months at the time of the first febrile seizure.

Most febrile seizures occur in the first few hours of a fever, during the initial rise in body temperature.

Giving your child medications

Giving your child infants' or children's acetaminophen (Tylenol, others) or ibuprofen (Advil, Motrin, others) at the beginning of a fever may make your child more comfortable, but it won't prevent a seizure.

Use caution when giving aspirin to children or teenagers. Though aspirin is approved for use in children older than age 3, children and teenagers recovering from chickenpox or flu-like symptoms should never take aspirin. This is because aspirin has been linked to Reye's syndrome, a rare but potentially life-threatening condition, in such children.

Prescription prevention medications

Rarely, prescription anticonvulsant medications are used to try to prevent febrile seizures. However, these medications can have serious side effects that may outweigh any possible benefit.

Rectal diazepam (Diastat) or nasal midazolam might be prescribed to be used as needed for children who are prone to long febrile seizures. These medications are typically used to treat seizures that last longer than five minutes or if the child has more than one seizure within 24 hours. They are not typically used to prevent febrile seizures.

Febrile seizures occur in children with normal development. Your doctor will carefully review your child's medical history and developmental history to exclude other risk factors for epilepsy. In normally developing children, identifying the cause of your child's fever is the first step after a febrile seizure.

Simple febrile seizures

Children who are current with their vaccinations who have a first simple febrile seizure don't need testing. Your doctor can diagnose the febrile seizure based on history.

In children with a delayed vaccination schedule or a compromised immune system, your doctor may recommend tests to look for severe infections:

• A blood test
• A urine test
• A spinal tap (lumbar puncture), to find out if your child has a central nervous system infection, such as meningitis

Complex febrile seizures

To diagnose the cause of a complex febrile seizure, your doctor may also recommend an electroencephalogram (EEG), a test that measures brain activity.

Your doctor may also recommend an MRI to check your child's brain if your child has:

• An unusually large head
• An abnormal neurological evaluation
• Signs and symptoms of increased pressure in the skull
• A febrile seizure that lasted an unusually long time

Most febrile seizures stop on their own within a couple of minutes. If your child has a febrile seizure, stay calm and follow these steps:

• Place your child on his or her side on a soft, flat surface where he or she won't fall.
• Start timing the seizure.
• Stay close to watch and comfort your child.
• Remove hard or sharp objects near your child.
• Loosen tight or restrictive clothing.
• Don't restrain your child or interfere with your child's movements.
• Don't put anything in your child's mouth.

Call for emergency medical attention if:

• Your child has a febrile seizure that lasts more than five minutes.
• Your child has repeated seizures.
• Your child's seizure lasted less than five minutes but your child isn't improving quickly.

More-serious episodes

A doctor may order medication to stop a seizure that lasts longer than five minutes.

Your child's doctor may hospitalize the child for observation if:

• The seizure is prolonged
• The child is younger than 6 months old
• The seizure is accompanied by a serious infection
• The source of the infection can't be found

But a hospital stay isn't usually necessary for simple febrile seizures.

You're likely to start by seeing your child's family doctor or pediatrician. You may then be referred to a doctor who specializes in disorders of the brain and nervous system (neurologist).

Here's some information to help you get ready for your appointment.

What you can do

• Write down everything you remember about your child's seizure, including signs or symptoms that occurred before the seizure, such as a fever.
• List medications, vitamins and supplements your child takes.
• Write down questions to ask your doctor.

For febrile seizures, some basic questions to ask your doctor include:

• What's the most likely cause of my child's seizure?
• What tests does my child need? Do these tests require special preparation?
• Is this likely to happen again?
• Does my child need treatment?
• Will giving my child fever-reducing medications during an illness help prevent febrile seizures?
• What should I do the next time my child has a fever?
• What can I do to help my child during a febrile seizure?
• My child has another health condition. How can we manage them together?
• Are there brochures or other printed material I can take? What websites do you recommend?

Don't hesitate to ask other questions, as well.

What to expect from your doctor

Your doctor is likely to ask you a number of questions, such as:

• Did your child have a fever or illness before having this seizure?
• Can you describe your child's seizure? What were the signs and symptoms? How long did the seizure last?
• Has this happened before?
• Does anyone in your family have a history of febrile seizures or seizure disorders?
• Has your child been exposed to illnesses?
• Does your child have a history of head trauma or a neurological disease?

What you can do in the meantime

If your child has another febrile seizure:

• Don't restrain your child, but do place him or her on a safe surface, such as the floor.
• Place your child on his or her side, keeping the face to the side and the lower arm extended under the head, to prevent your child from inhaling vomit if vomiting occurs.
• If your child had anything in his or her mouth when the seizure began, remove it to prevent choking. Don't put anything in your child's mouth during a seizure.
• Seek emergency care for a seizure that lasts longer than five minutes.