Propylene Glycol (PG) is one of the most widely used multifunctional ingredients worldwide. It serves as a solvent, carrier, humectant, stabilizer, and processing aid in applications ranging from pharmaceuticals and personal care products to food flavorings and industrial formulations.
Due to its wide range of applications, many manufacturers assume that obtaining USP-grade Propylene Glycol is sufficient to meet the needs of all international markets. Indeed, USP compliance is an important benchmark of quality. However, companies seeking to enter the Japanese market often discover that meeting USP requirements is only part of the standards.
Japan maintains its own regulatory framework for ingredients used in quasi-drugs, and understanding the differences between USP specifications and Japanese requirements can help suppliers avoid delays, reduce qualification risks, and improve customer confidence.
USP (United States Pharmacopeia) is one of the world's most recognized pharmacopeial standards. USP-grade Propylene Glycol is widely accepted for pharmaceutical, food, and cosmetic applications because it meets stringent requirements for purity and safety.
Typical USP testing includes identification, Assay, Specific gravity, Acidity or alkalinity, Chloride content, Sulfate content, Heavy metals, Residue on ignition, Water content, and organic impurities.
For many international buyers, a USP certificate immediately signals a high level of manufacturing quality and process control. As a result, USP has become a global commercial language for ingredient quality.
However, compliance with USP does not automatically guarantee acceptance in every regulatory environment around the world.
One reason for this difference is Japan's regulatory system itself. Unlike many countries that classify products simply as pharmaceuticals or cosmetics, Japan maintains a third category known as quasi-drugs. Quasi-drugs occupy a position between cosmetics and pharmaceuticals.
In Japan, ingredients used in quasi-drugs are regulated under the Japanese Standards of Quasi-Drug Ingredients 2021 (JSQI 2021), commonly referred to as Gai-Gen-Ki (外原規). Published by the Ministry of Health, Labour and Welfare (MHLW), JSQI 2021 establishes quality specifications, identification tests, purity requirements, assay methods, and general analytical procedures for ingredients used in quasi-drug products.
As the principal technical standard supporting Japan's unique quasi-drug regulatory framework, JSQI 2021 serves as an essential reference for manufacturers, importers, and suppliers seeking access to the Japanese market. The current edition covers more than 2,600 ingredients and has undergone several revisions to align with evolving regulatory and quality-control requirements.
Typical examples according to JSQI 2021 include medicated skin care products, Whitening products, Anti-acne formulations, Hair growth products, Medicated shampoos, Oral care products, Deodorants, and antiperspirants. Because these products may claim specific functional benefits, the ingredients used within them are subject to additional regulatory oversight.
For propylene glycol used for similar drug applications, even if the material has already met the standards of the US Pharmacopeia, it may still need to be examined further to comply with the relevant specifications of Japan.
The issue is not that USP standards are lower than Japanese standards. In fact, comparing strictness directly can be misleading. The more important point is that the two systems were designed for different purposes. USP was developed as a pharmacopeial standard intended to support pharmaceutical quality globally; Japanese quasi-drug specifications were developed specifically to support regulatory evaluation and product approval within Japan.
Consequently, certain quality attributes may be evaluated differently. Even when the same property is being tested, differences may exist in various fields including analytical methodology, sample preparation, acceptance criteria, and reporting requirements. A manufacturer may therefore possess a high-quality USP-grade product while still needing additional documentation or testing to demonstrate compliance with Japanese expectations.
One of the most overlooked aspects of regulatory compliance is the test method itself. Many suppliers focus exclusively on numerical specifications.
For example, a customer may ask:"What is the chloride content?” or "What is the specific gravity?"
While the numerical result is important, Japanese customers frequently pay equal attention to how the result was obtained. The same quality parameter can be evaluated through different analytical procedures depending on the applicable standard.
When qualification teams review supplier documentation, they often compare both the test result and the testing methodology against local requirements. As a result, suppliers who can provide detailed analytical references frequently gain a competitive advantage during customer audits and supplier approval processes.
Over the past decade, global competition among raw material suppliers has intensified significantly.
Most reputable manufacturers can already produce Propylene Glycol that meets high purity standards. As product quality becomes increasingly standardized, purchasing decisions are often influenced by factors beyond the product itself.
Customers now evaluate suppliers based on regulatory support, documentation quality, responsiveness, supply chain transparency, and technical expertise.
In many cases, the supplier capable of answering regulatory questions quickly and accurately gains an advantage over competitors offering similar material quality. For companies exporting to Japan, understanding quasi-drug requirements has therefore become more than a compliance exercise—it has become a commercial advantage.
When discussing specifications with Japanese customers, many overseas suppliers focus on proving that their product meets USP.
While this is certainly valuable, customers are often asking a different question: what about our regulatory framework?
This subtle difference changes the entire conversation. The objective is not simply to demonstrate product quality. The objective is to demonstrate suitability for the intended market.
Customers want confidence that the supplier understands: Japanese regulatory expectations, Documentation requirements, Quality assurance practices, Long-term compliance support.
A supplier who understands these requirements becomes more than a vendor. Instead, they become a partner.
(Figure: Propylene Glycol (PG): structure of the world production by country, 2013)
For manufacturers and distributors of Propylene Glycol, the Japanese market offers significant opportunities, particularly in personal care and quasi-drug applications. However, success requires more than producing a material that meets USP specifications.
We should consider the following:
1. Complying with Japanese specifications alongside USP requirements.
2. Preparing supporting regulatory documentation.
3. Positioning compliance support as part of the overall value proposition.
USP-grade Propylene Glycol remains one of the most trusted quality benchmarks in the global marketplace.
Nevertheless, suppliers entering the Japanese quasi-drug sector should recognize that USP compliance alone may not always satisfy local expectations.
The challenge is rarely about product quality itself.
Instead, it is about demonstrating compliance within a different regulatory framework and providing the documentation and technical support necessary for successful market entry.
As international supply chains continue to evolve, suppliers who understand both global standards and local requirements will be best positioned to support customers and create long-term partnerships.
In today's regulatory environment, quality is no longer defined solely by the product in the container. It is also defined by the knowledge, documentation, and support that accompany it.
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