Reye's syndrome


Reye's syndrome, also known as Reye syndrome, is a rare but serious condition that causes swelling in the liver and brain. Reye's syndrome can occur at any age but usually affects children and teenagers after a viral infection, most commonly the flu or chickenpox.

Symptoms such as confusion, seizures and loss of consciousness need emergency treatment. Early diagnosis and treatment of Reye's syndrome can save a child's life.

Aspirin has been linked with Reye's syndrome, so use caution when giving aspirin to children or teenagers for fever or pain. Though aspirin is approved for use in children older than age 3, children and teenagers recovering from chickenpox or flu-like symptoms should never take aspirin.

For the treatment of fever or pain, consider giving your child infants' or children's acetaminophen (Tylenol, others) or ibuprofen (Advil, Motrin, others). They're safer alternatives to aspirin. Talk to your health care provider if you have concerns.


In Reye's syndrome, a child's blood sugar usually drops while levels of ammonia and acidity in the blood rises. The liver also may swell, and fats may build up. Swelling may occur in the brain. This can cause seizures, convulsions or loss of consciousness.

The symptoms of Reye's syndrome usually start about 3 to 5 days after the onset of a viral infection. This may be the flu, known as influenza, or chickenpox. Or Reye's syndrome may develop after an upper respiratory infection such as a cold.

Initial symptoms

For children younger than age 2, the first symptoms of Reye's syndrome may include:

  • Diarrhea.
  • Rapid breathing.

For older children and teenagers, early symptoms may include:

  • Vomiting that doesn't stop.
  • Being sleepy or sluggish.

Additional symptoms

As the condition progresses, symptoms may become more serious, including:

  • Irritable, aggressive or irrational behavior.
  • Confusion or seeing or hearing things that aren't there.
  • Weakness in the arms and legs or not being able to move them.
  • Seizures.
  • Excessive sluggishness.
  • Decreased level of consciousness.

These symptoms need emergency treatment.

When to see a doctor

Early diagnosis and treatment of Reye's syndrome can save a child's life. If you suspect that your child has Reye's syndrome, it's important to act quickly.

Seek emergency medical help if your child:

  • Has seizures.
  • Loses consciousness.

Contact your child's health care provider if your child experiences the following after a bout with the flu or chickenpox:

  • Vomits repeatedly.
  • Becomes unusually sleepy or sluggish.
  • Has sudden behavior changes.


The use of aspirin during a viral illness has most commonly been linked to Reye's syndrome. But the exact cause of Reye's syndrome is unknown. Several factors may play a role.

In some cases, the symptoms of Reye's syndrome may be caused by another health condition such as an underlying metabolic disorder. This can occur even without the use of aspirin.

The most frequent of these rare disorders is medium-chain acyl-CoA dehydrogenase (MCAD) deficiency. MCAD deficiency is a fatty acid oxidation disorder. Fatty acid oxidation disorders are a group of inherited metabolic disorders in which the body is unable to break down fatty acids. This happens because an enzyme is missing or not working properly. In people with a fatty acid oxidation disorder, aspirin use during a viral illness is more likely to trigger symptoms of Reye's syndrome. A screening test can determine if your child has a fatty acid oxidation disorder.

Reye's syndrome may develop after influenza or chickenpox in particular.

Exposure to certain toxins — such as insecticides, herbicides and paint thinner — may produce symptoms similar to Reye's syndrome. But these toxins don't cause Reye's syndrome.

Risk factors

The following factors — usually when they occur together — may increase your child's risk of developing Reye's syndrome:

  • Using aspirin to treat a viral infection such as flu, chickenpox or an upper respiratory infection.
  • Having an underlying metabolic disorder. This may include a fatty acid oxidation disorder or another disorder of mitochondrial function.


Most children and teenagers who have Reye's syndrome survive. However, varying degrees of lasting brain damage are possible. Without proper diagnosis and treatment, Reye's syndrome can cause death within a few days.


Use caution when giving aspirin to children or teenagers. Though aspirin is approved for use in children older than age 3, children and teenagers recovering from chickenpox or flu-like symptoms should never take aspirin. This includes plain aspirin and medicines that contain aspirin.

Some hospitals and medical facilities screen newborns for fatty acid oxidation disorders to determine which children are at greater risk of developing Reye's syndrome. Children with known fatty acid oxidation disorders should not take aspirin or aspirin-containing products.

Always check the label before you give your child medicine. This includes products you buy without a prescription and alternative or herbal remedies. Aspirin can show up in some unexpected products such as Alka-Seltzer.

Sometimes aspirin goes by other names, such as:

  • Acetylsalicylic acid.
  • Acetylsalicylate.
  • Salicylic acid.
  • Salicylate.

For the treatment of fever or pain related to the flu, chickenpox or another viral illness, consider giving your child a safer alternative to aspirin. This may include infants' or children's acetaminophen (Tylenol, others) or ibuprofen (Advil, Motrin, others).

There's an exception to the general rule about aspirin. Children and teenagers who have certain chronic diseases, such as Kawasaki disease, may need long-term treatment with medicines that contain aspirin.

If your child needs to take aspirin, make sure your child's vaccines are current. This includes two doses of the chickenpox vaccine and a yearly flu vaccine. Avoiding these two viral illnesses can help prevent Reye's syndrome.


There's no specific test for Reye's syndrome. Screening usually begins with blood and urine tests. It also may include testing for fatty acid oxidation disorders and other disorders.

Sometimes other tests are needed to check for other possible causes of liver problems or problems with the nervous system. For example:

  • Spinal tap, also known as a lumbar puncture. A spinal tap can help identify or rule out other diseases with similar symptoms. A spinal tap can uncover an infection of the lining that surrounds the brain and spinal cord, known as meningitis. Or it can help diagnose inflammation or an infection of the brain, called encephalitis.

    During a spinal tap, a needle is inserted through the lower back into a space between two bones. A small sample of the fluid that surrounds the brain and spinal cord is removed and sent to a lab for analysis.

  • Liver biopsy. A liver biopsy can help identify or rule out conditions that may be affecting the liver. In people with Reye's syndrome, a liver biopsy can show a buildup of fats in liver cells.

    During a liver biopsy, a needle is inserted through the skin on the upper right side of the abdomen and into the liver. A small sample of liver tissue is removed and sent to a lab for analysis.

  • CT scan or MRI. A head CT scan or MRI scan can help identify or rule out other causes of behavior changes or decreased alertness. These tests may show swelling in the brain, which may be caused by Reye's syndrome.

    A CT scan uses a series of X-rays taken from different angles to create a detailed image of the brain. An MRI scan uses a strong magnetic field and radio waves rather than X-rays to generate images of the brain.

Lumbar puncture, also known as a spinal tap


Reye's syndrome is usually treated in the hospital. Severe cases may be treated in the intensive care unit. The hospital staff will closely monitor your child's blood pressure and other vital signs. Specific treatment may include:

  • Intravenous (IV) fluids. Sugar — also called glucose — and an electrolyte solution may be given through an IV line.
  • Diuretics. These medicines may be used to decrease pressure from fluids around the brain. Diuretics also increase fluid loss through urination.
  • Medicines to prevent bleeding. Bleeding due to liver problems may require treatment with vitamin K, plasma and platelets.
  • Cooling blankets. These blankets help maintain internal body temperature at a safe level.

A breathing machine called a ventilator can help if your child has trouble breathing.

Preparing for an appointment

Reye's syndrome is often diagnosed in an emergency situation. This is because of the serious symptoms caused by Reye's syndrome, including seizures or loss of consciousness. In some cases, early symptoms prompt an appointment with a health care provider.

Your child is likely be referred to a specialist in conditions of the brain and nervous system, known as a neurologist.

Because appointments can be brief and there's often a lot to cover, it can help to be well prepared. Here are some tips to help you get ready for your appointment.

What you can do

  • Be aware of any pre-appointment restrictions. At the time you make the appointment, ask if there's anything you need to do in advance.
  • Write down any symptoms your child is experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
  • Make a list of all medicines, including vitamins, dietary supplements and medicines you can buy without a prescription that your child has taken. Be sure to list any medicines containing aspirin. Even better, take the original bottles and a written list of the dosages and directions.
  • Take along a family member or friend. It can be difficult to recall all the information provided to you during an appointment. The person who accompanies you may remember something that you forgot or missed.
  • Write down questions to ask your health care provider. Don't be afraid to ask questions or to speak up when you don't understand something your provider says.

List your questions from most important to least important to make the most of your time with your child's health care provider. For Reye's syndrome some basic questions to ask include:

  • What are other possible causes for my child's symptoms?
  • What tests are needed to confirm the diagnosis?
  • What are the treatment options and the pluses and minuses for each?
  • What results can I expect?
  • What kind of follow-up should I expect?

In addition to the questions that you've prepared to ask your health care provider, don't hesitate to ask questions during your appointment.

What to expect from your doctor

The neurologist is likely to ask about your child's symptoms and history of viral illnesses. The neurologist also may conduct a medical exam and schedule tests to gather information about your child's condition and to rule out other diseases, such as meningitis or encephalitis.

Content From Mayo Clinic Updated: 02/15/2023
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