Researchers in France claim to have discovered a natural painkiller in human saliva.

The research has indicated that the natural painkiller been shown to be more potent than morphine.

The discovery of the painkiller in saliva, known as opiorphin, could lead to improved pain medications as it is a naturally occurring molecule that is quickly metabolised in the body.

The researcher, from Pasteur Institute in Paris, are doing further research on the painkiller on how the substance is produced in the body.

The discovery was made after the researchers identified a powerful pain-inhibiting molecule in rats.

The study was published in the Proceedings of the National Academy of Sciences.