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Ask Dr. K: Febrile seizures usually have no long-term effects

DEAR DOCTOR K: My 9-month-old daughter had a seizure last time she had a high fever. The pediatrician said it could happen again. What do I need to know?

DEAR READER: The medical term for what your daughter experienced is febrile seizure. I was taught that febrile seizures are caused by a high fever or a sudden rise in body temperature. The effect of the higher body temperature makes the brain “irritable” and causes a seizure. But in the last few years, we’ve learned it may be more complicated than that.

Some childhood seizures are caused by a new infection with a common virus, called human herpesvirus-6. This virus infects most children at a young age and remains in their bodies for the rest of their lives.

When a child first is infected with this virus, it travels to the brain, where it causes a fever – and may cause chemical changes in the brain that lead to seizures. We don’t know how many febrile seizures are caused by this virus. We do know that severe febrile seizures that don’t end promptly often are caused by the virus.

Depending on where in the brain the seizure starts, and whether the electrical firestorm travels to another part of the brain, seizures have different effects on the body. Some seizures cause a person to temporarily lose consciousness. Some cause different muscles in the body to twitch or jerk uncontrollably. Others just cause temporary strange behavior.

As your doctor mentioned, many children who have had a febrile seizure will have another one. One of the best ways to prevent one is to prevent a high fever. If your daughter develops a fever, have her drink plenty of water and fruit juices to prevent dehydration. Give her ibuprofen (Advil, Motrin, others) or acetaminophen (Tylenol), but not aspirin.

Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.


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