The University of Rennes team hope the findings could lead to ways to predict when people will have a seizure.
These could include dogs or "electronic noses" that pick up the precise odour being given off during a seizure.
Dogs have previously been shown to be able to sniff out diseases including cancers, Parkinson's, malaria and diabetes.
- Epilepsy is caused by disruption to the electrical signals in the brain causing seizures
- The disease can run in families or be caused by a stroke or oxygen deprivation at birth
Some people with epilepsy already rely on the animals.
One sleeping in a child's bedroom can alert family members of a seizure in the middle of the night.
The latest study, in the journal Scientific Reports, trained five dogs from Medical Mutts, in the US, to recognise the smell of sweat taken from a patient having a seizure.
They were then given a choice of seven sweat samples taken from other patients while they were either relaxing, exercising or having a seizure.