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It occurs primarily in children, although some cases have been reported in adults. Although Reye's syndrome is serious and often fatal, it is rare. The number of cases of Reye's syndrome in the United States has declined 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's 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 three to seven days after the chickenpox or flu is one of the primary symptoms of Reye's 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, you should seek immediate medical help. In infants, the symptoms of Reye's syndrome may not include vomiting.

Reye's syndrome usually occurs when a child is recovering from a viral illness. It can develop as early as a few days after the viral illness begins, however. Although doctors do not know what causes the syndrome to develop, research has found that children who take aspirin products during the viral illness are at higher risk for Reye's syndrome. That's why you should avoid giving children and teens aspirin (acetylsalicylic acid) or products that contain sodium or bismuth salicylates. Check the labels on over-the-counter (OTC) medications carefully; the FDA requires that products containing these substances carry a warning label. This is a partial list of OTC medications that contain aspirin or similar salicylates: Pepto Bismol, Excedrin, Alka-Seltzer, Dristan Tablets, Bufferin, and Triaminicin.

It may also be confused with encephalitis or a psychiatric 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, when influenza and other viral respiratory illnesses are prevalent.

ALT is an enzyme found mainly in liver cells, although 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's syndrome have increased levels of certain liver enzymes, including ALT. Other liver enzyme tests are also generally done to check for liver damage. Persistent vomiting after a viral infection, along with elevated liver enzymes, may indicate a case of Reye's syndrome. Other possible causes of liver problems, including rare inherited disorders that can mimic Reye's syndrome, would also need to be eliminated.

There is no cure for Reye's syndrome. A child who develops the condition and early on is monitored carefully for proper fluid and electrolyte balance has a good chance for recovery. Those who are not diagnosed early enough may develop brain damage or a coma. When Reye's syndrome was first officially identified, the death rate was 80 percent, according to the National Reye's Syndrome Foundation. Today, the death rate is approximately 50 percent.