When body temperature rises because of an infection or inflammation, this can cause a febrile seizure or febrile convulsion. It does not mean the person has epilepsy. Febrile seizures can occur at any age but are more common in children.

Febrile seizures affect around 4% of children at some time between the age of 3 months and 5 years but are most common around the age of 2 years. They commonly occur with an infection. The child may have a higher temperature than usual when the seizure happens, or they may develop a fever later. In most cases, the fever will be above 101°F (38.3°C).

One in three children who have a febrile seizure will experience at least one more during childhood.

Seizures can look alarming to parents or caregivers, but most seizures are harmless and do not indicate a long-term medical problem. A brief febrile seizure lasts up to 15 minutes, but a prolonged seizure will be over 15 minutes. If a child with a high temperature has a seizure and does not have a previously diagnosed neurological or developmental issue, it will most likely be a febrile seizure.

Here, learn more about why febrile seizures happen, how to recognize them, what they mean, and what to do if one occurs.

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There are two types of febrile seizures.

A simple febrile seizure lasts under 15 minutes and does not happen again in the next 24 hours. It is the most common type, accounting for around 75% of cases.

A complex febrile seizure involves at least one of the following:

  • lasting longer than 15 minutes
  • occurring again within 24 hours
  • starting on one side of the body

After either type of seizure, there may be drowsiness, but the person usually recovers fully in a few minutes. If this does not happen, it may mean there are underlying complications that need further investigation.

A doctor may also recommend further tests if the person had a sudden headache, a change in consciousness, weakness, or other symptoms before the seizure started.

Complex seizures are less common than simple seizures.

Seizures can happen for various reasons, but a febrile seizure occurs because of a fever. They usually occur as the person’s temperature is rising but may appear before.

Many common infections can trigger a febrile seizure, such as:

  • flu
  • a cold
  • tonsillitis
  • an ear infection
  • less commonly, pneumonia, a kidney infection, or meningitis

Febrile seizures are more common with viral than bacterial infections. Researchers note links with a virus known as HHV6 in the United States and Europe, and the influenza A virus in Asian countries.

Do vaccinations cause seizures?

In rare cases, a febrile seizure can occur after a vaccination, according to the Centers for Disease Control and Prevention (CDC). The overall risk is up to 30 seizures in every 100,000 children vaccinated.

The CDC notes that they can occur 5–12 days after the first dose of the measles, mumps, and rubella (MMR) or the measles, mumps, rubella, and varicella (MMRV) vaccine. They can also occur within 24 hours of having the 13-valent conjugate (PCV13) vaccine or diphtheria, tetanus, acellular pertussis (DTaP) vaccine. There is no evidence that the flu shot will cause a seizure.

However, the risk of any long-term impact of a febrile seizure is low unless there is an underlying reason for other seizures to occur.

Doctors encourage immunization and urge parents and caregivers to complete the vaccination schedule, even if a child has febrile seizures after a jab. This is because the risks and complications of diseases, such as measles, are far greater.

A febrile seizure often happens at the beginning of an illness, as the fever starts, and often before other signs of illness appear.

During a simple seizure, the following may occur:

  • The person looks hot and flushed.
  • Their eyes appear to roll back.
  • Their body becomes stiff and then twitches or shakes.
  • The person becomes unresponsive.
  • They may urinate.

This usually lasts only a few seconds and usually less than 5 minutes. After, the person may be drowsy for a few minutes but feel better after an hour or so.

A complex febrile seizure may look different:

  • The seizure will last longer than 15 minutes.
  • It may happen again within 24 hours.
  • Full recovery takes longer than one hour.
  • Movements or twitching will affect one part of the body, such as a limb, rather than the whole body.

While a fever can trigger a febrile seizure, severe symptoms during the seizure do not necessarily mean the person’s fever is very high.

A seizure needs urgent medical attention if:

  • There are other severe symptoms, including breathing difficulties.
  • The child is under 6 months old.
  • The seizure lasts longer than 5 minutes.
  • The person is a child who has not had a seizure before.
  • The person lost consciousness before the seizure started.
  • One seizure starts as soon as another finishes.
  • The person does not feel better within an hour after the seizure starts.

Sometimes an infection can involve a seizure that is not febrile, for example, meningitis. This is an infection of the lining of the brain and may have a neurological impact.

Learn more about the signs and symptoms of meningitis.

If a person needs medical attention following a febrile seizure, a doctor will look first for signs of an infection.

This may include:

  • blood tests
  • urine tests
  • in some cases, such as suspected meningitis, taking some spinal fluid

For a complex febrile seizure, the doctor may carry out other tests to rule out underlying conditions.

If a child has a febrile seizure, a caregiver can help by:

  • noting the time it started
  • laying them on their side in the recovery position, with their head tilted slightly back to keep their airway open
  • avoid putting anything in their mouth
  • after the seizure, helping cool the child by removing clothing, if the room is warm
  • giving acetaminophen or ibuprofen when they recover, if they can drink some water

A caregiver should stay with the child and call a doctor if they have concerns.

If the seizure lasts longer than 5 minutes, someone should seek emergency medical help.

Medical treatment

A person will not need treatment for a simple febrile seizure, but they may need treatment for an underlying infection.

If they have a complex seizure, a doctor will likely investigate to check for an underlying condition. If there is, they will recommend the appropriate treatment.

In some cases, if a seizure lasts for some time, a doctor may use medication to stop it. This may include putting a rapidly acting medication, such as diazepam or midazolam, into the person’s rectum, nose, or mouth or injecting it into a vein.

What should you do if a toddler develops a rash after a fever?

In most cases, the best way to prevent a febrile seizure is to take measures to avoid infection.

This includes:

  • following a doctor’s instructions about using acetaminophen or ibuprofen to help manage a fever
  • following recommendations for routine vaccinations
  • practicing good hygiene, such as handwashing
  • seeking early treatment if a child develops symptoms that could indicate an infection

If a febrile seizure occurs before the age of 12 months, there is around a 50% chance that another one may occur. If it happens within the second year, the risk drops to around 30%. A child may also have a higher risk if they have a low-grade fever before the first seizure or if two seizures happen within a relatively short time.

Learn more about seizures in babies.

A febrile seizure is different from an epileptic seizure, but some children who experience a febrile seizure lasting longer than 15 minutes receive a diagnosis of epilepsy later in life.

Epilepsy is a separate condition with a different cause.

Epilepsy is more likely if:

  • Underlying neurological features relating to epilepsy are present.
  • There was a developmental delay before febrile seizures started.
  • There is a family history of epilepsy.
  • The seizure is complex.

Around 1–2% of children who have simple febrile seizures develop epilepsy, which is slightly higher than in the general population.

A febrile seizure will not cause developmental delay or affect intelligence, experts say.

Febrile seizures are common among children under the age of 5 years and usually accompany a fever.

A febrile seizure can be alarming to parents and caregivers but does not usually have serious consequences. A seizure usually accompanies an infection, which may need treatment.

In some cases, a child who has a prolonged seizure may later receive a diagnosis of epilepsy, but this is not the case for most febrile seizures.

Anyone who has concerns about a seizure or recurring seizures should seek medical advice, as treatment may be necessary in some cases.