Fever seizures (febrile seizures) are uncontrolled muscle spasms and unresponsiveness in a child that are caused by a rapid increase in body temperature. They usually last 1 to 3 minutes and are seldom serious.

Fevers that lead to a fever seizure may develop so quickly that parents did not even realize that their child's temperature was rising. Once a fever has reached a high temperature, the risk of a seizure is probably over.

Fever seizures are not a form of epilepsy. A seizure is likely to be fever-related if it meets the following criteria:

• The seizure happened within 24 hours of the start of a fever.
• The seizure lasted less than 3 to 5 minutes.
• The seizure affected the entire body, not just one side of the body.
• The child is between 6 months and 6 years old.
• The child does not have nervous system (neurological) problems.
• The child has had fever seizures before.