In the latest round of testing products purchased on Amazon, supplement manufacturer NOW found widespread potency failures in oregano oil supplements.

The results revealed that nearly two-thirds of the products failed potency testing, and six had no detectable levels of carvacrol, the active component in oregano oil. Many of the softgel samples “contained virtually no oregano smell or taste,” the company reported, which should be an immediate red flag.

NOW purchased two bottles of oregano oil from each brand in February 2026, and had them tested internally, along with parallel testing from Eurofins, a 17025-accredited independent lab. Its own products were also tested against those bought on Amazon.

Oregano (Origanum vulagaris) is a popular aromatic herb whose oil is used to maintain a healthy intestinal flora balance, attributed to the main active compound, carvacrol, which is typically present in oregano oil at levels between 55% and 90%.

Testing Methodology

Carvacrol was quantified by HPLC (High Performance Liquid Chromatography) using a validated reverse-phase method. Out of 35 tested brands, 14 met label claims for carvacrol, and 15 brands had less than 8% of carvacrol claimed on label. Six products contained no detectable carvacrol. NOW’s oregano oil liquid and softgel products were among those that met label claims.

NOW reported that non-specific testing methods like spectrophotometric assays can be fooled by other constituents of oregano oil, like thymol. These methods could artificially inflate potency results. HPLC, however, can separate and identify carvacrol from closely-related compounds, providing a more accurate measure of product quality.

Responsibility Lies with Everyone in the Supply Chain

According to NOW, “a cursory glance at these products suggested that many were produced by the same companies, most likely as contract/private label manufacturers. Even when manufactured by a contract manufacturer, the responsibility of providing safe, quality products lies equally with everyone in the supply chain and rigorous testing should be performed at every ‘link’ in that chain.”

“NOW’s in-house analytical testing paired with Eurofins’ independent verification underscores the importance of scientifically valid methods,” said Katie Banaszewski, NOW senior director of quality. “NOW will continue to purchase and test products sold on major online platforms and publicly share the results to encourage higher quality standards across the supplement industry.”