There is no known cause of Reye syndrome. It is most often seen in children ages 4 to 12. Most cases that occur with chickenpox are in children ages 5 to 9. Cases that occur with the flu are most often in children ages 10 to 14.

Children with Reye syndrome get sick very suddenly. The syndrome often begins with vomiting. It may last for many hours. The vomiting is quickly followed by irritable and aggressive behavior. As the condition gets worse, the child may be unable to stay awake and alert.

Other symptoms of Reye syndrome:

• Confusion
• Lethargy
• Loss of consciousness or coma
• Mental changes
• Nausea and vomiting
• Seizures
• Unusual placement of arms and legs (decerebrate posture). The arms are extended straight and turned toward the body, the legs are held straight, and the toes are pointed downward

Other symptoms that can occur with this disorder include:

• Double vision
• Hearing loss
• Muscle function loss or paralysis of the arms or legs
• Speech difficulties
• Weakness in the arms or legs

The following tests may be used to diagnose Reye syndrome:

• Blood chemistry tests
• Head CT or head MRI scan
• Liver biopsy
• Liver function tests
• Serum ammonia test
• Spinal tap

There is no specific treatment for this condition. The health care provider will monitor the pressure in the brain, blood gases, and blood acid-base balance (pH).

Treatments may include:

• Breathing support (a breathing machine may be needed during a deep coma)
• Fluids by IV to provide electrolytes and glucose
• Steroids to reduce swelling in the brain

How well a person does depends on the severity of any coma, as well as other factors.

The outcome for those who survive an acute episode may be good.

Complications may include:

• Coma
• Permanent brain damage
• Seizures

When untreated, seizures and coma may be life threatening.

Go to the emergency room or call the local emergency number (such as 911) immediately if your child has:

• Confusion
• Lethargy
• Other mental changes

Never give a child aspirin unless told to do so by your child's provider.

When a child must take aspirin for a medical condition, take care to reduce the child's risk of catching a viral illness, such as the flu and chickenpox. Avoid aspirin for several weeks after the child has received a varicella (chickenpox) vaccine.

Note: Other over-the-counter medicines, such as Pepto-Bismol and substances with oil of wintergreen also contain aspirin-like compounds called salicylates. DO NOT give these to a child who has a cold or fever.

Reye's syndrome

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Barkoudah E. Encephalopathies. In: Kliegman RM, St. Geme JW, Blum NJ, et al, eds. Nelson Textbook of Pediatrics. 22nd ed. Philadelphia, PA: Elsevier; 2025:chap 638.

Cherry JD. Reye syndrome. In: Cherry JD, Harrison GJ, Kaplan SL, Steinbach WJ, Hotez PJ, eds. Feigin and Cherry's Textbook of Pediatric Infectious Diseases. 8th ed. Philadelphia, PA: Elsevier; 2019:chap 50.

Updated by: Neil K. Kaneshiro, MD, MHA, Clinical Professor of Pediatrics, University of Washington School of Medicine, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.