Of the 35 products tested, only 14 met the label claim for carvacrol, the active measurable component in oregano oil, while six had no detectable levels of whatsoever of the compound, NOW reported.
The Illinois-based company purchased two samples of each oregano oil supplement (including NOW brand) in February 2026 to conduct internal analyses. It also partnered with Eurofins, an ISO 17025-accredited independent laboratory, to ensure accuracy and transparency.
Oregano (Origanum vulgaris) is a popular, aromatic herb whose oil is used to maintain healthy intestinal flora balance.
“We are seeing double-digit YOY growth for our oregano oil SKUs, which seems to align with category growth,” Katie Banaszewski, senior director of quality at NOW, told NutraIngredients.
Carvacrol is responsible for the oil’s beneficial properties, and genuine oregano oils reportedly contain 55% to 90% carvacrol.
Using HPLC (High-Performance Liquid Chromatography) with a validated reverse-phase method, the analysis showed that only 14 of the 35 tested brands met the label claim for carvacrol. Fifteen brands had less than 8% of label claim and six of those had no detectable carvacrol. NOW Oregano Oil liquid and softgels were among the few samples that met the label claim for carvacrol, according to the report.
“This round of testing was disappointing, with nearly two-thirds of the brands failing carvacrol testing,” Banaszewski said. “NOW’s in-house analytical testing paired with Eurofins’ independent verification underscores the importance of scientifically valid methods.”
Production and formulation
According to NOW, many of the products appeared to be produced by the same companies, most likely as contract/private label manufacturers. NOW noted that, 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.
The company stated that choosing the correct testing method for carvacrol is important because non-specific methods, such as spectrophotometric assays, can be fooled by the other constituents of oregano oil, like thymol. These methods may artificially inflate potency results, making products seem compliant when they are not. In contrast, HPLC can separate and identify carvacrol from closely related compounds. NOW’s and Eurofin’s testing both relied on chromatographic specificity.
Additionally, many of the oregano oil products on Amazon also contain black seed (Nigella sativa) oil, which is known to contain carvacrol as a minor component.
“We can fairly assume the majority of any present carvacrol comes from oregano oil in formulations containing both oregano oil and black cumin seed oil,” Banaszewski said. “We could have assumed ~2.5% carvacrol contribution from black cumin seed oil, but this is an unknown variable and would not necessarily be fair to factor this in, so if anything, the study erred on the side of being generous. In other words, we should have expected a higher amount of carvacrol in these formulations than we called for in the report.”
Banaszewski confirmed that NOW will share its findings with Amazon. NutraIngredients contacted Amazon for comment but did not receive a reply prior to publication.
Testing
This is NOW’s 22nd round of product analysis since it initiated its testing program in 2017 to evaluate lesser-known brands sold online. All rounds to date have raised concerns tied to issues such as potency, labeling, contamination, adulteration and heavy metals across product categories.
NOW’s ongoing efforts to publicize quality concerns about supplements purchased on Amazon were recognized by NutraIngredients with the 2021 NutraIngredients-USA Award for Industry Initiative of the Year.
“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,” Banaszewski said.
