Causes of febrile seizures  

Febrile seizures are linked to fevers, but the exact cause is unknown.

Some researchers think that the biological processes associated with a high temperature may be responsible.

A high temperature is thought to be caused by a bacterial or viral infection that stimulates the release of cytokines. Cytokines are proteins that affect the parts of the brain and nervous system responsible for regulating the body’s temperature. Their release causes a rise in the body's temperature.

One theory is that in certain people, high levels of cytokines may temporarily ‘scramble’ the workings of the brain and nervous system, triggering a seizure.

Family history

Although febrile seizures are poorly understood, a family history of the conditions is thought to increase the risk. 

If a child has a first-degree relative (mother, father, sister or brother) with a history of febrile seizures, their risk of having seizures increases. The more relatives affected, the higher the risk.

This is probably the result of one or more genetic mutations that a child inherits from their parents, which makes them more susceptible to seizures. A genetic mutation means the instructions carried in certain genes become ‘scrambled’, resulting in some of the body’s processes not working in the normal way.

Associated infections

Most febrile seizures occur when a child has a high temperature caused by an infection. The three most common infections associated with febrile convulsions are:

Other infections associated with febrile seizures are:


In rare cases, febrile seizures can occur after a child has a vaccination. Research has shown that your child has a one in 3,000 to 4,000 chance of having a febrile seizure after having the MMR vaccine.

The risks are even lower with the DTaP/IPV/Hib vaccine – a one in 11,000 to 16,000.

Most febrile seizures occur when a child has fever caused by a common infection such the flu, chickenpox or tonsillitis  

When to seek medical help

Febrile seizures are fairly common in children and, although they can be frightening, they aren't usually a cause for concern.

In very rare cases, a seizure can be a sign of a more serious condition, such as meningitis, which requires emergency medical treatment.

Dial 999 immediately to request an ambulance if your child:

  • is having a seizure that's lasting longer than five minutes and showing no signs of stopping
  • has a blotchy red rash that doesn't fade or change colour when a glass is placed against it (in some cases a rash isn't always present)
  • is having breathing difficulties

Read more about the signs and symptoms of meningitis.

Page last reviewed: 06/10/2014

Next review due: 06/10/2016