Reye's syndrome (RS) is primarily a children's disease, although it can occur at any age. It affects all organs of the body but is most harmful to the brain and the liver. The syndrome causes an acute increase of pressure in the brain and often massive accumulations of fat in the liver and other organs. RS is defined as a two-phase illness because it generally occurs in conjunction with a previous viral infection, such as the flu or chicken pox. The disorder commonly occurs during recovery from a viral infection, although it can also develop three to five days after the onset of the viral illness. RS is often misdiagnosed as encephalitis, meningitis, diabetes, drug overdose, poisoning, sudden infant death syndrome, or a psychiatric illness. The symptoms of RS include persistent or recurrent vomiting; listlessness; personality changes such as irritability or combativeness and disorientation or confusion; delirium, convulsions, and loss of consciousness. If these symptoms are present during or soon after a viral illness, medical attention should be sought immediately. The symptoms of RS in infants do not follow a typical pattern; for example, vomiting does not always occur. Epidemiologic evidence indicates that aspirin (salicylate) is the major preventable risk factor for RS. The mechanism by which aspirin and other salicylates trigger RS is not completely understood. A "Reye's-like" illness may occur in children with genetic metabolic disorders and other toxic disorders. A physician should be consulted before giving a child any aspirin or antinausea medicines during a viral illness, which can mask the symptoms of RS.
This answer is based on source information from the National Institute of Neurological Disorders and Stroke
Of unknown cause, the syndrome has occurred with the use of aspirin to treat chickenpox or the flu in children. There are other products on the market which may contain an ingredient similar to aspirin (salicylates). It is always good policy to read over the counter medication labels before giving them to your child or teenager. Pepto-Bismol and substances with oil of wintergreen also contain these aspirin compounds called salicylates. The syndrome has become very uncommon since aspirin is no longer recommended for routine use in children.
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