Health Library

Febrile Seizures

What Causes Febrile Seizures?

Febrile seizures are thought to be caused by the body’s response to a rapid rise in temperature and release of inflammatory cytokines (proteins) in children 6 months to 5 years old, with the highest risk between 9 months and 18 months old. Triggers include infections (bacterial, like strep throat, or a virus, like the flu) or some immunizations. Sometimes, a seizure can happen after a child gets certain vaccines, especially the MMR (measles, mumps, rubella) shot. But vaccine-related fevers and seizures are rare and usually mild.

There is also a genetic link to febrile seizures. A child is more likely to have one if a parent or sibling has had them. Still, most febrile seizures are not a sign of a serious condition.

What Are the Signs and Symptoms of Febrile Seizures?

A febrile seizure usually starts suddenly and lasts for less than five minutes. Signs may include:

• A high fever (usually over 100.4°F or 38°C)
• Eye rolling
• Loss of consciousness or responsiveness
• Shaking or jerking movements that are rhythmic, non-suppressible, and stereotyped (looking the same)
• Trouble breathing or skin turning blue (rare)

There are two types of febrile seizures:

• Simple febrile seizures: The most common type of febrile seizure. Simple febrile seizures last less than 15 minutes, have full body shaking and do not happen again within 24 hours.
• Complex febrile seizures: These last longer than 15 minutes, happen more than once in 24 hours or only affect one side of the body. These types of seizures increase the risk of epilepsy slightly.

How Are Febrile Seizures Diagnosed?

Doctors usually diagnose febrile seizures by asking about the child’s symptoms and health history. A physical exam will check for signs of infection or other causes.

Tests are not usually needed. But in some cases, a doctor may order:

• A lumbar puncture (spinal tap) if meningitis is suspected
• Blood tests or urine tests to check for infection
• Imaging tests like a CT scan or MRI if the seizure was complex or unusual

What Are the Treatment Options for Febrile Seizures?

Most febrile seizures stop on their own within a few minutes. During a seizure, it’s important to stay calm and take the following steps:

• Lay your child on their side on a soft surface.
• Do not put anything in their mouth.
• Loosen tight clothing.
• Call your doctor or seek care if it’s your child’s first seizure.

If the seizure lasts more than five minutes, call 911.

Children who have had febrile seizures usually don’t need daily medicine. But a doctor may prescribe a rescue medicine to use during long seizures. Children who have had a complex febrile seizure may need further testing.

Prognosis for Febrile Seizures

Most children who have febrile seizures fully recover. They do not usually develop epilepsy or other brain problems. Febrile seizures do not cause brain damage.

Are Febrile Seizures Dangerous?

No, febrile seizures are not usually dangerous, but they can be upsetting to see.

How Many Febrile Seizures Is Too Many?

Some children may have more than one seizure. There is no set number for how many are too many, but if your child has frequent or complex febrile seizures, their doctor may do a more in-depth examination.

What Are the Long-Term Effects of Febrile Seizures?

In most cases, there are no long-term effects of febrile seizures. But some children who have complex febrile seizures are at an increased risk of developing epilepsy.

How Common Are Febrile Seizures?

Febrile seizures are one of the most common types of seizures in children. About 1 in 25 children will have one by age 5.

Your child’s doctor can explain what to expect and how to prepare in case another seizure happens.