Kao’s voluntary recall of its Oribe Serene Scalp Densifying Shampoo in the US and Canada offers salutary lessons for personal care formulators on preservation strategies and testing, according to ‘The Green Chemist’ Dr Barbara Olioso.
Batches of Kao USA’s premium scalp care product were withdrawn due to the detection of Pluralibacter gergoviae bacteria.
Though Pluralibacter gergoviae bacteria pose little medical risk to healthy people, said Kao, those with certain health issues such as weakened immune systems may be more susceptible to infection by the bacteria.
The recall is limited to specific lots of the Oribe Serene Scalp Densifying Shampoo in 8.5 oz and 33.8 oz sizes.
Further investigation to confirm the scope of the issue is still ongoing.
In a blog post, UK-based Italian consultant Olioso said the recall offers a number of key lessons for formulators.
The shampoo is preserved primarily with phenoxyethanol - a combination, she said, which “sits at the heart of a well-documented but underappreciated microbiological vulnerability”.
“Phenoxyethanol is an excellent broad-spectrum preservative for the vast majority of microbial challenges a cosmetic formulation will encounter. Its vulnerability to P. gergoviae is specific and well-documented.
“Formulators building preservation systems on a phenoxyethanol foundation need to ask: what in my system provides genuine gram-negative coverage if the phenoxyethanol is being metabolised by this organism? If the answer is “caprylyl glycol and sodium benzoate at pH 5.5”, the gap needs to be addressed with either additional actives, pH adjustment, or supplementary challenge data against P. gergoviae specifically.
Olioso also said P. gergoviae must be an explicit target in challenge testing because is not in the standard ISO 11930 panel and will not be detected at batch release by routine microbiological testing.
“For any aqueous product preserved with phenoxyethanol, parabens, or caprylyl glycol-based systems, including P. gergoviae as an additional challenge organism is not optional — it is scientifically necessary,” she added.
The organism’s documented adaptive resistance to cosmetic preservatives and its established pattern of causing recalls makes it an objectionable organism that should be treated as such in all preservative efficacy testing protocols, regardless of regulatory requirement, said Olioso.
Other key takeaways from the voluntary recall were said to include: the need to establish and maintain the exact pH at which a formulation operates — across batch-to-batch variation and across shelf life; the importance of manufacturing environmental monitoring that is specific enough to identify short-duration contamination windows before they reach finished product; and periodic post-market microbiological surveillance.
