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For more than a century, aspirin was used to help safely relieve the symptoms of everything from headaches to stomach cramps. But in households with children, this commonplace medication is a potentially dangerous drug. That's because the use of aspirin has been linked with Reye's syndrome — a rare but serious illness that can affect the blood, liver and brain of children and teenagers recovering from a viral infection.

In Reye's syndrome, the level of ammonia and acidity in the blood typically rises while the level of blood sugar drops. At the same time, the liver may swell and develop fat deposits. Swelling also may occur in the brain and can cause emergency symptoms such as seizures or convulsions. Reye's syndrome can eventually lead to a coma and brain death.

The incidence of Reye's syndrome has declined greatly since a peak in 1980. Many people assume the decline is due to the warnings against children taking aspirin, but that may be only part of the reason.

Better tests can diagnose metabolic conditions formerly thought to be Reye's syndrome. Today children who develop Reye's syndrome or conditions once thought to be Reye's syndrome receive an earlier diagnosis and better treatment, which help improve recovery and reduce complications.

The signs and symptoms of Reye's syndrome typically begin about one week after a viral infection such as influenza or chickenpox. After a child appears to be recovering from a viral illness, he or she may suddenly become much more seriously ill.

Children first tend to exhibit these signs:

• Persistent nausea and vomiting
• Decline in mental alertness
• Unusual sleepiness or lethargy
• Disoriented behavior
• Combative behavior

The onset of Reye's can be rapid, and signs and symptoms may worsen within hours.

As Reye's syndrome progresses, children may develop even more serious signs, including:

• Weakness or paralysis in extremities
• Loss of consciousness
• Seizures or convulsions

These signs and symptoms require emergency treatment.

Reye's syndrome tends to occur in previously healthy children about a week after common viral infections such as influenza or chickenpox. It can also develop after an ordinary upper respiratory infection such as a cold. The precise reason is unknown, but using aspirin to treat a viral illness or infection may trigger the condition in children.

Reye's syndrome may be a metabolic condition — one without symptoms (asymptomatic) — that's unmasked by viral illnesses. Reye's syndrome occurs most commonly in children between the ages of 4 and 12.

Reye's syndrome can develop rapidly, so it's important to take prompt action if you suspect your child has the condition. Call your child's doctor if your child becomes unusually sleepy or lethargic or begins to exhibit sudden mental changes or combative behavior following a bout with influenza or chickenpox. If your child loses consciousness or has convulsions or seizures, seek emergency medical assistance immediately.

If your child becomes sick with a possible case of Reye's syndrome, doctors may want to check blood tests of his or her liver function. They may also want to evaluate other possible causes of liver problems and investigate any neurological abnormalities. In addition to blood and urine tests, diagnostic procedures may include:

• Spinal tap (lumbar puncture). This procedure helps to rule out other diseases with similar signs and symptoms, such as infection of the lining and fluid that surround your brain and spinal cord (meningitis) or inflammation or infection of the brain (encephalitis). Local anesthesia is used to numb the puncture site in the lower back. A needle is then inserted through the lower back into the space around the spinal cord to collect a small sample of cerebrospinal fluid (CSF). The CSF can be analyzed for protein, sugar, and red and white blood cells. The sample is also routinely cultured to identify bacterial and viral infections.
• Liver biopsy. Generally, this procedure is done by inserting a thin needle through the skin on the upper right side of the abdomen and into the liver in order to draw a tissue sample from the liver for laboratory analysis. This analysis is then used to rule out other possible diseases that may be affecting the liver.

Detecting rare metabolic disorders
Your doctor also may want to evaluate the possibility that your child has one of the rare, inherited metabolic disorders that can mimic the signs and symptoms of Reye's syndrome. The list of these metabolic disorders is long, and most of them have long unfamiliar terms, such as medium-chain acyl-CoA dehydrogenase (MCAD) deficiency. Most, if not all, of these conditions are inherited and may occur with varying degrees of severity in other family members.

The key to diagnosing or excluding these unusual conditions is obtaining blood and urine samples during the acute phase of the illness and having them analyzed in a qualified biochemical genetics laboratory. Many of these metabolic conditions are termed mitochondrial diseases because the problems arise from the part of body cells called the mitochondria.

If a child dies of a Reye's-like illness, it may be important to obtain blood and urine to check for these metabolic conditions. Collecting samples of liver and brain tissue shortly after death could be the key to diagnosing a condition that might affect other family members. It may even be possible to analyze tissue from an autopsy done many years ago to clarify whether a death was due to a metabolic cause.

While most children who survive Reye's syndrome don't suffer any long-term damage, this disorder can occasionally result in permanent liver damage, irreversible nervous system damage, coma and death.

Reye's syndrome may include a combination of the following problems:

• High levels of ammonia and acidity and a low level of sugar in the blood (hypoglycemia)
• Fatty deposits in the liver and abnormal liver function tests
• Poor blood clotting and bleeding caused by liver failure
• Swelling of the brain, sometimes with coma and brain death

Earlier diagnosis and treatment can greatly reduce the chance of death.

Fortunately, most children whom doctors evaluate for possible signs and symptoms of Reye's syndrome don't have the disease. Instead, they may not have fully recovered from a flu-like illness, or they may be dealing with complications of dehydration. Children who receive a diagnosis of Reye's syndrome, however, may require admission to a pediatric intensive care unit. Drug treatments may include:

• Intravenous fluids. These may include glucose to increase low blood sugar; electrolyte solutions containing sodium, potassium and chloride to correct blood chemistry values; and basic solutions to treat acidity.
• Insulin. Small amounts of insulin can increase sugar metabolism.
• Corticosteroids. A corticosteroid medication can reduce brain swelling and inflammation.
• Diuretics. A diuretic, such as mannitol, can increase fluid loss through urination and help reduce brain swelling.

Your doctor may want to continuously monitor your child's blood pressure using a thin, flexible tube (arterial catheter). An arterial catheter is threaded into an artery and is commonly used to monitor blood gases and acidity, as well as blood pressure.

If Reye's syndrome reaches an advanced stage, treatment may include the use of a ventilator to help assist a child with breathing.

To reduce the risk of Reye's syndrome, avoid giving aspirin or medications that contain aspirin to your child to treat viral illnesses. Other names for aspirin include:

• Acetylsalicylic acid
• Acetylsalicylate
• Salicylic acid
• Salicylate

If your child or teenager has the flu or chickenpox, use other medications such as acetaminophen (Tylenol, others), ibuprofen (Advil, Motrin, others) or naproxen sodium (Aleve) to reduce fever or relieve pain. Unless specifically advised by your child's doctor, don't give aspirin to anyone younger than 19. Check the label on any medication you're going to give your child, because aspirin can show up in some unexpected places. Some products that contain aspirin include Alka-Seltzer, some Excedrin products and Pepto-Bismol. Also, check with your doctor before giving your child any alternative or folk remedies. Some of these also contain aspirin. If a full ingredient list isn't available, don't give the medicine to your child without checking with your doctor first.

Some children with chronic diseases, such as juvenile rheumatoid arthritis, may need treatment long term with drugs that contain aspirin. Doctors advise that these children receive the varicella (chickenpox) and influenza vaccines to reduce their risk of developing Reye's syndrome. In fact, the varicella vaccine is now recommended for all healthy children between 12 and 15 months old. It's also recommended that children between six and 24 months of age receive the influenza vaccine each October. Never having these two diseases helps prevent Reye's syndrome.