Dogs can detect a telltale scent linked to epileptic seizures, scientists have discovered, raising the possibility that they could be trained to reliably warn owners when a seizure is imminent.

The findings may also help explain anecdotal reports that dogs are able to sense when their owner is about to have a seizure. Knowing when a seizure is going to occur could allow people with epilepsy to have greater control and independence, meaning they could take measures to avoid injury, seek help or take medication.

Amélie Catala, of the University of Rennes in France and the paper’s first author, said: “At the moment there are anecdotes that some people report dogs alert them before a seizure, but we don’t have any strong evidence in the scientific literature.”

She said it was also unclear whether, in such cases, the dogs relied on visual cues or subtle changes in behaviour or smell, and whether the cues were the same from one person to the next.

In the latest study, published in the journal Scientific Reports, Catala and colleagues wanted to test whether specially trained dogs could distinguish breath and body odour samples taken from epileptic patients during a seizure from samples taken during normal conditions and following an exercise session. Before the testing sessions, the dogs were trained to target seizure samples. They were then tested using samples taken from five patients with different forms of epilepsy.

The dogs’ ability to detect positives ranged from 67% to 100%, while their ability to correctly identify negatives ranged from 95% to 100%. The results suggest that seizures are associated with certain specific odours, regardless of the type of seizure or the background body odour of the patient.

The scientists are now planning to test whether this telltale odour preceded the seizure, potentially allowing dogs to be trained to reliably alert owners to seizures.

A spokeswoman for the charity Epilepsy Action said that some people already relied on their dogs to predict seizures. “We still don’t know whether they do that by smell or some other sense,” she said. “So this research is interesting and could be a next step in understanding how dogs can further support people living with uncontrolled epilepsy.”

Rita Howson, the chief executive of Support Dogs, a charity that trains dogs to help people with autism, epilepsy and other conditions, said: “Dogs are very good observers of humans. Dogs know what is going to happen when you pick up their leash – their behaviour indicates this. Their behaviour can also change when they pick up on more subtle cues – maybe a smell or behavioural change in the client that occurs before an oncoming seizure.”