Reye's syndrome is a very rare condition that can affect children or young adults after they've had an illness like flu or chickenpox. It can cause serious brain problems if it's not treated quickly.

Symptoms of Reye's syndrome often start 1 to 3 weeks after a child recovers from a virus like flu or chickenpox.

The child may:

• keep being sick (vomiting)
• be drowsy and lack energy
• feel confused
• have changes in their behaviour, such as being irritable or aggressive
• breathe quickly and have a fast heart rate
• have fits (seizures)
• lose consciousness

Reye's syndrome most commonly affects children between 5 and 14 years of age.

Younger and older children can also sometimes get it, but it's very rare in babies under the age of 1 and in those over the age of 18.

Call 999 or go to A&E if your child:

Ask for an urgent GP appointment or get help from NHS 111 if:

If there's a chance your child might have Reye's syndrome, they'll be referred to a specialist for some tests.

Tests may include:

• blood and urine tests
• a CT scan and an electroencephalogram (EEG)
• a lumbar puncture – where a thin needle is inserted into their lower back to remove a small amount of spinal fluid for testing
• a liver biopsy – where a small sample of cells from the liver is taken for testing

If your child has Reye's syndrome, they'll need to go into hospital straight away for treatment.

Treatments for Reye's syndrome may include:

• help with breathing using an oxygen machine
• fluids given directly into a vein to help prevent dehydration
• medicines to help treat and manage symptoms

Most children with Reye's syndrome make a full recovery if it's treated quickly. But some children can have long-term brain problems.

The exact cause of Reye's syndrome is unknown.

It's been linked to the use of a type of medicine known as salicylates, particularly aspirin, in young people and children under 16.

Sometimes a child with a rare genetic condition, such as medium-chain acyl-CoA dehydrogenase deficiency (MCADD), can get Reye's syndrome. This has nothing to do with the use of aspirin.

There are things you can do to reduce your child's chance of getting Reye's syndrome.