Consumer groups in Australia and the UK have found dried oregano products aren’t always the real deal. The products can also contain olive and sumac leaves.

Last year, UK consumer group Which? reported a quarter of 78 dried oregano samples tested by a food fraud expert were adulterated. A subsequent study by Australian consumer group Choice found just five out of 12 products were 100 percent oregano. Seven contained olive leaves and two also contained sumac leaves.

Non-oregano ingredients made up between 50 and 90 percent of the adulterated samples detected by Choice. “Someone, somewhere along the oregano supply chain, has made a conscious decision to substitute other leaves for oregano – but without more information, we can only speculate as to why,” it said.

Choice tested only one sample from each brand and says the results aren’t necessarily representative. But the findings indicate potential breaches of consumer law and it’s referred the matter to the Australian Competition and Consumer Commission (ACCC) which is investigating.

The ACCC investigation may also shed light on products here as retailers of dried oregano may source supplies from the same producers.

Herbs have been identified as highly vulnerable to food fraud. But detecting adulterated products by sight is extremely difficult because the ingredients are typically chopped or ground.