My 18-month-old son recently had a simple febrile seizure. I had no idea what was happening. It was terrifying! His doctor says that he's all right now, but I'm still worried about lasting brain damage. I also feel guilty for not noticing his fever. How can I prevent this terror from happening again?

Some children have seizures or convulsions when they have fevers. Although febrile seizures are fairly common, many parents have never seen one until it happens to their child. Febrile seizures occur in 3% to 5% of otherwise healthy children between the ages of 6 months and 5 years. Toddlers are the most commonly affected.

The seizure begins with the sudden sustained contraction of muscles on both sides of a child's body -- usually the muscles of the face, the trunk, the arms and the legs. Often a haunting, involuntary cry or moan emerges from the child, from the force of the muscle contraction. The contraction continues for seemingly endless seconds, or tens of seconds. The child will fall, if standing, and may pass urine. He may vomit. He may bite his tongue. The child will not be breathing, and may begin to turn blue. Finally, the sustained contraction is broken by repeated brief moments of relaxation -- the child's body begins to jerk rhythmically. The child is unresponsive to the parent's screams.

This is usually one of lifetime's most frightening moments for the parents. Most parents are afraid that their child will die or will have brain damage. Thankfully, simple febrile seizures are harmless.

Febrile seizures are brought on by the sudden stimulation of many brain cells at once. Experts argue over whether febrile seizures are triggered by the height of the fever or by the rate of rise. I suspect that both play a role. Most febrile seizures occur well within the first 24 hours of an illness, not necessarily when the fever is highest. Often the seizure is the first sign of a fever, making febrile seizures hard to prevent.

A simple febrile seizure stops by itself within a few seconds to 10 minutes, sometimes followed by a brief period of drowsiness or confusion. Anticonvulsant medicines are generally not needed.

A complex febrile seizure is one that lasts longer than 15 minutes, occurs in an isolated part of the body, or recurs during the same illness.

During the seizure leave your child on the floor, although you may want to slide a blanket under him if the floor is hard. Move him only if he is in a dangerous location. Loosen any tight clothing, especially around the neck. If possible, open or remove clothes from the waist up. If he vomits, or if saliva and mucus build up in the mouth, turn him on his side or stomach. Don't try to restrain your son, or stop the seizure movements. Don't try to force anything into his mouth to prevent him from biting his tongue, as this increases the risk of injury and choking. Be sure that your child is breathing during the seizure. If he appears blue around his lips, you should call 911 immediately.

Focus your attention on bringing the fever down. Inserting rectal acetaminophen (Tylenol) is a great first step -- if you happen to have some. Don't try to give him anything by mouth.

Apply cool washcloths to the forehead and neck. Sponge the rest of his body with lukewarm (not cold) water. (Cold water or alcohol may make him shiver and make the fever worse). After the seizure is over and your son is awake, give him the normal dose of ibuprofen (Motrin or Advil) or acetaminophen (Tylenol). Children should see a doctor as soon as possible after their first febrile seizure. If the seizure ends quickly, drive him to an emergency room when it is over.