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A febrile seizure is a convulsion in young children caused by a sudden spike in body temperature, often from an infection. Watching your child experience a febrile seizure can be alarming. The seizure may only last a few minutes, though it may seem like an eternity.

Fortunately, febrile seizures aren't as dangerous as they may look. A seizure triggered by a sudden fever is usually harmless and typically doesn't indicate a long-term or ongoing problem. Often, a febrile seizure occurs before parents even realize that their child is ill.

Febrile seizures affect 2 percent to 4 percent of children between the ages of 6 months and 5 years. Although fairly common, a febrile seizure is still reason to seek medical attention, especially to check for any serious cause for the fever.

If your child is prone to febrile seizures, you might be able to prevent them by treating a fever early. However, most febrile seizures develop suddenly and without warning. Being sure the child is safe during a seizure, offering comfort afterwards and following up with a doctor's visit are good approaches for handling a febrile seizure.

Signs and symptoms of a febrile seizure can range from mild — rolling of the eyes — to more severe shaking or tightening of the muscles.

The child having a febrile seizure may:

• Have a fever — usually higher than 102 F
• Lose consciousness
• Shake or jerk the arms and legs on both sides of the body
• Roll his or her eyes back in the head
• Have trouble breathing
• Lose urine
• Vomit
• Cry or moan

Febrile seizures are classified as simple or complex:

• Simple febrile seizures. These are the most common. They last from a few seconds to 15 minutes and stop on their own. After the seizure, your child may cry, act confused, or be quite sleepy.
• Complex febrile seizures. These are more serious. A complex febrile seizure lasts longer than 15 minutes, occurs more than once within 24 hours or is confined to one side of your child's body.

Although a febrile seizure is usually caused by a rapid rise in your child's temperature, the severity of the signs and symptoms doesn't necessarily reflect the level of the fever.

Most febrile seizures occur because of a sudden spike in body temperature, and most occur during the first day of a fever. But a febrile seizure also may develop as the fever is declining.

Usually, the fevers that trigger febrile seizures are caused by an infection in your child's body. The most common cause is a typical childhood illness, such as a middle ear infection or roseola — a viral infection that causes swollen glands and a rash. A less common but very serious cause of sudden fever and febrile seizures is an infection of a child's brain and spinal cord (central nervous system), such as meningitis or encephalitis.

The risk of febrile seizures also increases after common childhood immunizations. Febrile seizure is a rare side effect of immunization, but it may occur the day of the diphtheria, tetanus and acellular pertussis (DTaP) vaccination or eight to 14 days after a measles-mumps-rubella (MMR) vaccination. Febrile seizures are caused by the fever that may accompany the vaccination — not by the vaccination itself.

Young age is the strongest risk factor. About 2 percent to 4 percent of children have a febrile seizure before their fifth birthday. Most febrile seizures occur in children between the ages of 6 months and 5 years and are particularly common in toddlers. Children rarely develop their first febrile seizure before the age of 6 months or have them after 3 years of age. Febrile seizures usually stop by the time a child is 5 or 6 years old. Some children inherit a family's tendency to have seizures with a fever.

Have a first-time febrile seizure evaluated by your doctor as soon as possible, even if it lasts only a few seconds. If the seizure ends quickly, call your doctor as soon as it's over and ask when and where your child can be examined. If the seizure lasts longer than five minutes or is accompanied by vomiting, problems with breathing or extreme sleepiness, call for an ambulance to take your child to the emergency room.

Your doctor will examine your child to determine the possible causes of the fever and seizure. Your doctor may order blood and urine tests to detect an infection.

If your doctor suspects a central nervous system infection, a spinal tap (lumbar puncture) may be necessary. In this procedure, a doctor inserts a needle into your child's lower back to remove a small amount of spinal fluid. This test can reveal evidence of infection in the fluid that surrounds the brain and spinal cord. Further tests may be necessary if your child suffered a complex febrile seizure.

Although febrile seizures may cause great fear and concern for parents, most febrile seizures produce no lasting effects. Simple febrile seizures don't cause brain damage, mental retardation or learning disabilities, and they don't mean your child has a more serious underlying disorder, or epilepsy.

Epilepsy in children is defined as recurring seizures in the absence of fever. The odds that your child will develop epilepsy after a febrile seizure are small. Only a small percentage of children who have a febrile seizure go on to develop epilepsy, but not because of the febrile seizures. Children with epilepsy sometimes have their first seizures during fevers.

The most common complication of febrile seizures is the possibility of more febrile seizures. About a third of children who have a febrile seizure will have another one with a subsequent fever. The risk of recurrence is higher if your child had a low fever at the time of the first febrile seizure, if the period between the start of the fever and the seizure was short, or if an immediate family member has a history of febrile seizures. But the biggest factor affecting recurrence is age. The younger a child is when the first febrile seizure occurs, the more likely he or she is to have more.

It's not necessary to lower your child's fever to stop a febrile seizure. So don't try to give your child fever medications during a seizure. For the same reason, you don't need to place your child in a cooling tub of water. It's much more practical, more comfortable — and safer — for your child to remain lying on the carpet or a bed.

Most febrile seizures stop on their own within five minutes. If your child has a febrile seizure that lasts more than five minutes — or if your child has two or more seizures — call for emergency medical attention.

In rare cases, the seizure may continue until your child arrives at the emergency room. If this happens, a doctor may order medication that's administered either through your child's rectum or intravenously to stop the seizure. If the seizure is prolonged or accompanied by a serious infection or if the source of the infection can't be determined, your doctor may want your child to stay in the hospital for further observation. But a hospital stay isn't routinely necessary for simple febrile seizures.

Most of the time, a febrile seizure occurs the first day of an illness. Often, a febrile seizure occurs before parents realize that their child is ill.

Giving your child acetaminophen (Tylenol, others) or ibuprofen (Advil, Motrin, others) at the first indication of fever will help reduce the fever, but won't necessarily prevent a seizure. You can also help control fever by making sure your child drinks plenty of fluids and not bundling him or her up too tightly at night.

Don't give aspirin to a child. Aspirin may trigger a rare but potentially fatal disorder known as Reye's syndrome.

Rarely, prescription medications are used to prevent febrile seizures. Anticonvulsant medications such as phenobarbital, valproic acid (Depakene) and divalproex sodium (Depakote) can prevent febrile seizures when taken daily. Oral or rectal diazepam (Valium, Diastat) also can reduce the risk of febrile seizures if taken at the time of a fever. But these medications all have drawbacks. They carry a definite risk of serious side effects in young children. Doctors rarely prescribe these prevention medications because most febrile seizures are harmless and most children outgrow them without any problems.

If your child has a febrile seizure, stay calm and follow these steps to help your child during the seizure:

• Place your child on his or her side, somewhere where he or she won't fall.
• Stay close to watch and comfort your child.
• Remove any hard or sharp objects near your child.
• Loosen any tight or restrictive clothing.
• Don't restrain your child or interfere with your child's movements.
• Don't attempt to put anything in your child's mouth.

If possible, try to time the seizure using your watch or a clock. Because they're so alarming, seizures often seem to last longer than they really do. Also try to note which part of your child's body begins to shake first, and look for other signs of illness. This can help your doctor understand the cause of the seizure.

Within one to two hours of a febrile seizure, many children are back on their feet, running around the doctor's office or playing safely at home. By staying calm, observing your child and knowing when to call the doctor, you're doing everything that's needed to take care of your child.