It occurs mainly in children, although some cases have been reported in adults. Reye syndrome is serious and often fatal. But it is rare. The number of cases of Reye syndrome in the U.S. has fallen sharply since parents have been warned not to give children aspirin or products containing aspirin. Children who take aspirin seem to be at higher risk for developing the condition.

Although Reye syndrome affects all the organs in the body, it does the greatest damage to the brain and liver. It causes a severe increase in pressure in the brain and massive accumulations of fat in the liver.

Vomiting that begins 3 to 7 days after the chickenpox or flu is one of the main symptoms of Reye syndrome. The vomiting usually becomes more and more severe over the next 12 hours. Other symptoms include listlessness, disorientation, delirium, convulsions, and loss of consciousness. If a child has these symptoms, get medical help right away. In infants, the symptoms of Reye syndrome may not include vomiting.

Reye syndrome usually occurs when a child is recovering from a viral illness. But it can develop as early as a few days after the viral illness begins. Healthcare providers don't know what causes the syndrome to develop. But research has found that children who take aspirin products during the viral illness are at higher risk for Reye syndrome. That's why you should not give children or teens aspirin (acetylsalicylic acid) or products that contain sodium or bismuth salicylates. Check the labels on over-the-counter (OTC) medicines carefully. The FDA requires that products containing these substances carry a warning label.

It may also be confused with encephalitis or a mental illness, according to the NINDS.

The syndrome can occur at any time of year, but it is more likely to develop during January, February, and March. This is when the flu and other viral respiratory illnesses are common.

ALT was formerly called SGPT (serum glutamic pyruvic transaminase). It is an enzyme found mainly in liver cells. Smaller amounts are also in other organs of the body. When the liver becomes damaged, this enzyme leaks into the blood. A blood test can measure the level of ALT in the blood. Almost all cases of Reye syndrome have increased levels of certain liver enzymes, including ALT. Other liver enzyme tests are also generally done to check for liver damage. Lasting vomiting after a viral infection, along with high levels of liver enzymes, may mean a case of Reye syndrome. Other possible causes of liver problems, including rare inherited disorders that can mimic Reye syndrome, would also need to be eliminated.

There is no cure for Reye syndrome. A child who develops the condition and early on is monitored carefully for correct fluid and electrolyte balance has a good chance for recovery. Those who are not diagnosed early enough may develop brain damage or a coma.