Febrile seizures

July 23, 2018

Febrile seizures (febrile convulsions) are fits that can happen when a child has a fever. They most often happen between the ages of six months and three years.

It can be frightening and distressing to see your child having a seizure, particularly if it's their first one.

However, the fits are usually harmless and almost all children make a complete recovery afterwards.

As a precaution, you may still need to take your child to the nearest hospital or dial 999 for an ambulance – see the section 'What to do during a seizure'.

Signs of a febrile seizure

A febrile seizure usually lasts for less than five minutes. Your child will:

become stiff and their arms and legs may begin to twitch
lose consciousness and may wet or soil themselves

They may also vomit and foam at the mouth, and their eyes may roll back.

After the seizure, your child may be sleepy for up to an hour afterwards. A straightforward febrile seizure like this will only happen once during your child's illness.

Occasionally, febrile seizures can last longer than 15 minutes and symptoms may only affect one area of your child's body.

These are known as complex febrile seizures. The seizure sometimes happens again within 24 hours or during the period in which your child is ill.

What to do during a febrile seizure

If your child is having a febrile seizure, place them in the recovery position. Stay with your child and try to make a note of how long the seizure lasts.

Don't put anything into your child's mouth during a seizure – including medication – as there's a slight chance they might bite their tongue.

Take your child to the nearest hospital or dial 999 for an ambulance if:

your child is having a fit for the first time
the seizure lasts longer than five minutes and shows no signs of stopping
you suspect the seizure is being caused by another serious illness – for example, meningitis
your child is having breathing difficulties

While it's unlikely that there's anything seriously wrong, it's important to get your child checked.

If your child has had febrile seizures before and the seizure lasts for less than five minutes, phone your GP or NHS 111 for advice.

You should also contact your GP or NHS 111 if your child shows signs and symptoms of dehydration, a lack of fluid in the body.

This includes:

a dry mouth
sunken eyes
a lack of tears when crying
a sunken fontanelle – the soft spot usually found at the top of a young child's head

Seeing a doctor

Febrile seizures can often be diagnosed from a description of what happened. It's unlikely that a doctor will see the seizure, so it's useful to note:

how long the seizure lasted
what happened – such as body stiffening, twitching of the face, arms and legs, staring, and loss of consciousness
whether your child recovered within one hour
whether they've had a seizure before

Further tests, such as a blood or urine sample, may be needed if the cause of your child's illness isn't clear.

It can sometimes be difficult to get a urine sample from young children, so it may have to be done in hospital.

Further testing and observation in hospital is also usually recommended if your child's symptoms are unusual or they're having complex febrile seizures, particularly if they're younger than 12 months old.

The tests that may be recommended include:

an electroencephalogram (EEG) – this measures your child's electrical brain activity by placing electrodes on their scalp; unusual patterns of brain activity can sometimes indicate epilepsy
a lumbar puncture – where a small sample of cerebrospinal fluid (CSF) is removed for testing; CSF is a clear fluid that surrounds and protects the brain and spinal cord

A lumbar puncture can be used to determine whether your child has an infection of the brain or nervous system.

Causes of febrile seizures

The cause of febrile seizures is unknown, although they're linked to the start of a fever, a high temperature of 38C (100.4F) or above.

There may also be a genetic link to febrile seizures – the chances of having a seizure are increased if a close family member has a history of them.

In most cases, the high temperature is caused by an infection. Common examples are chickenpox, flu, a middle ear infection or tonsillitis.

In rare cases, febrile seizures can occur after a child has a vaccination.

Research has shown children have a 1 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 1 in 11,000 to 16,000 chance.

Recurring febrile seizures

About a third of children who have had a febrile seizure will have another one during a subsequent infection. This often happens within a year of the first one.

Recurrence is more likely if:

the first febrile seizure happened before your child was 18 months old
there's a history of seizures or epilepsy in your family
before having their first seizure, your child had a fever that lasted less than an hour or their temperature was under 40C (104F)
your child previously had a complex febrile seizure (more than one seizure during their illness)
your child attends a day care nursery – this increases their chances of developing common childhood infections, such as the flu or chickenpox

It's not recommended that your child is given a prescription of regular medicines to prevent further febrile seizures.

This is because the adverse side effects associated with many medicines outweigh any risks of the seizures themselves.

Research has shown the use of medication to control fever isn't likely to prevent further febrile seizures.

However, there may be exceptional circumstances where medication to prevent recurrent febrile seizures is recommended.

For example, children may need medication if they have a low threshold for having seizures during illness, particularly if the seizures are prolonged.

In this case, your child may be prescribed medications such as diazepam or lorazepam to take at the start of a fever.

Children who've had a febrile seizure after a routine vaccination – which is very rare – are no more at risk of having another seizure than those whose seizure was from illness.

Complications of febrile seizures

Febrile seizures have been linked to an increased risk of epilepsy, as well as other problems.

Recent research findings may indicate a link between febrile seizures and sudden unexplained death in childhood (SUDC), possibly because of the connection between febrile seizures and epilepsy.

But this link hasn't been proven and SUDC is incredibly rare, affecting around 1 in 100,000 children – equivalent to a 0.001% chance.

One of the biggest studies of its kind looked at more than 1.5 million children with a history of febrile seizures and found no evidence of an increased risk of death in later childhood or adulthood.