Febrile seizures are a relatively common childhood condition, referring to a child having a seizure (fit) when they have a high temperature of 38ºCF (100.4ºF) or above. This is usually the result of an infection.
Frightening but harmless
Watching a child having a seizure, particularly if they have no previous history of seizures, can be very frightening and distressing for the parents.
Many parents who have witnessed their child having a febrile seizure say they were convinced that their child was going to die. However, although febrile seizures may be very frightening, most are harmless and do not pose a threat to a child’s health.
What happens during a febrile seizure?
The cells in the brain, known as neurons, communicate with each other using electrical impulses. A seizure occurs when the electrical impulses become disrupted. This can cause the brain and the body to behave abnormally.
Most children have what is known as a tonic clonic seizure. During a tonic clonic seizure, the child's body becomes stiff, they lose consciousness and their arms and legs twitch. Some children may wet themselves.
Types of febrile seizure
There are two main types of febrile seizure:
- simple febrile seizure
- complex febrile seizure
Both types are discussed in more depth below.
Simple febrile seizure
A simple febrile seizure is the most common type of febrile seizure, accounting for about 9 out of 10 cases. A simple febrile seizure is a seizure that:
- is a tonic clonic seizure
- does not last longer than 15 minutes
- does not reoccur within 24 hours or during the period in which your child has an illness
Complex febrile seizure
Complex febrile seizures are less common than simple febrile seizures, accounting for 1 out of 10 cases. A complex febrile seizure is any seizure that has one or more of the following features:
- the seizure lasts longer than 15 minutes
- your child only has symptoms in one part of their body – this is known as a partial or focal seizure
- your child has another seizure within 24 hours of the first seizure or during the period in which they have an illness
- your child does not fully recover from the seizure within one hour
See Febrile seizures - symptoms for more information about simple and complex febrile seizures.
How common are febrile seizures?
Febrile seizures are quite common. An estimated 1 in 20 children will have at least one febrile seizure at some point. Most febrile seizures occur between the ages of six months and three years. The average age is 18 months.
The cause of febrile seizures is unknown, although the condition appears to run in some (but not all) families. Around 1 in 4 children who are affected by febrile seizures will have a family history of the condition. However, in half of all cases, there are no obvious causes or risk factors.
Febrile seizures and epilepsy
Many parents worry that if their child has one or more febrile seizures, they will develop epilepsy when they get older. Epilepsy is a condition where a person has repeated seizures (fits) without fever.
While it is true that children who have a history of febrile seizures have an increased risk of developing epilepsy, it should be stressed that the risk increase is still quite small.
For example, it is estimated that children with a history of simple febrile seizures have a 1 in 50 chance of developing epilepsy in later life. Children with a history of complex febrile seizures have a 1 in 20 chance of developing epilepsy in later life.
Outlook
The outlook for children with febrile seizures is excellent. Almost all children make a complete recovery, and there is not a single reported case of a child dying as the result of a febrile seizure.
In addition, one of the biggest studies of its kind looked at more than 1.5 million children with a history of febrile seizures. They found no evidence of an increased risk of death in later childhood or adulthood.
Tests may also be needed to identify what is causing the child’s high temperature. This is particularly the case in children who are under 12 months old and in those where there is no clinically obvious source of the fever.
There is no specific treatment for febrile seizures other than treating the underlying cause of the child’s high temperature, such as using antibiotics to treat an infection.
