Ask three laboratories how they test preservation and you may hear three different standards: Ph. Eur. 5.1.3, ISO 11930 and sometimes USP 51. They look similar on paper, so which one applies to your cosmetic product? This guide compares Ph. Eur. 5.1.3 and ISO 11930 side by side and tells you how to choose, so your challenge test report is accepted by your safety assessor and your customers.
Contents
- The short answer
- What each standard is
- What they have in common
- Where they differ
- What about USP 51?
- Which standard should you choose?
- Can I test with both?
- Do I need a challenge test at all?
- Common questions about the criteria
- What to put in your order
- How to document your choice in the PIF
- A worked example
- Practical advice when comparing quotes
- Why labs and assessors sometimes disagree
- A note on edition and amendments
- Frequently asked questions
- Key takeaways
The short answer
ISO 11930 is the standard written specifically for cosmetics and is the reference most EU safety assessors expect to see. Ph. Eur. 5.1.3 comes from the European Pharmacopoeia and was designed for pharmaceutical preparations. Both are valid scientific methods and use the same microorganisms and the same 28-day timeline, but ISO 11930 is the natural choice for a cosmetic placed on the EU market. If you are unsure, ask your safety assessor which one they want before you buy the test.
What each standard is
Ph. Eur. 5.1.3, Efficacy of Antimicrobial Preservation, is a general chapter of the European Pharmacopoeia. It checks the efficacy of the preservatives in pharmaceutical products and is referred to in monographs. It is not meant for routine batch control.
ISO 11930:2019, Cosmetics – Microbiology – Evaluation of the antimicrobial protection of a cosmetic product, is an international standard from ISO. It combines a preservation efficacy test with a method for microbiological risk assessment, which is based on ISO 29621.
Read also USP 51 Antimicrobial Effectiveness Test vs ISO 11930: US and EU
What they have in common
- Five test microorganisms: Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, Candida albicans and Aspergillus brasiliensis.
- A 28-day incubation with sampling at defined time points.
- Counts of surviving microorganisms, expressed as a log reduction.
- Two sets of acceptance criteria, A and B. Criteria A represent the recommended efficacy; criteria B are a lower level accepted only when A cannot be met for justified reasons.
Where they differ
- Origin and audience. Ph. Eur. is a pharmacopoeia for medicines; ISO 11930 is a cosmetics standard.
- Risk assessment. ISO 11930 links the test to a microbiological risk assessment and identifies low-risk products that may not need a challenge test.
- Product scope. ISO 11930 is designed mainly for water-soluble or water-miscible cosmetics and can be adapted when water is the internal phase.
- Acceptance criteria and details. The wording of the criteria and some method details differ, so a product can pass one and fail the other.
- Acceptance by assessors. Cosmetic safety assessors usually name ISO 11930 in the CPSR; a pharmacopoeia result is accepted by some and queried by others.
What about USP 51?
USP <51> is the United States Pharmacopeia chapter on antimicrobial effectiveness testing and is widely used for products sold in the US. It follows the same principle, with inoculation, sampling and acceptance criteria, but its details differ. At Cosmetic Testing Lab you can order the challenge test with either ISO 11930:2019 or USP 51.
Read also What Is a Cosmetic Challenge Test? Preservative Efficacy Testing Explained
Which standard should you choose?
- Selling cosmetics in the EU or UK: choose ISO 11930.
- Selling in the US: discuss USP 51 with your US partner or regulator, and consider ISO 11930 for the EU file.
- Product on the border with pharmaceuticals: follow the requirements of the category that applies to your product.
- Customer or retailer requirement: some customers specify the standard in their quality specification. Ask early.
Can I test with both?
Yes, and some brands do when they sell in several markets. Because the 28-day timelines run in parallel, two tests do not double the calendar time, though they do double the cost. Before doing so, check whether one standard already satisfies all your customers.
Do I need a challenge test at all?
ISO 11930 together with ISO 29621 allows low-risk products to be identified, such as those with very low water activity, high alcohol content or extreme pH. For these, a documented risk assessment may replace the test. The decision should be made by a qualified safety assessor, not assumed. Water-containing creams, lotions, serums and shampoos almost always need the test.
Read also Challenge Test Cost: What Affects the Price
Common questions about the criteria
- Is criteria A or B better? A is the target. B is a fall-back with a written justification.
- Is the passing result the same under both standards? Not necessarily. Read the standard’s criteria rather than assuming equivalence.
- Do I need to repeat the test if I change standard? A report is valid for the standard under which it was issued. If your assessor wants the other, you need a new test.
What to put in your order
When you order, state the standard, the product name, whether it contains water, the preservatives used and the packaging. The laboratory chooses the neutralisers and the inoculation method accordingly. Finished packaging and a near-final formula give the most reliable result.
How to document your choice in the PIF
Write down which standard you used, the edition, the laboratory and the date. Store the signed report and note the product, batch and formula it applies to. If an authority or a customer asks why you picked a standard, you can answer in one sentence. A short justification from your safety assessor in the CPSR is ideal.
A worked example
A brand makes a water-based face serum for the EU and plans a later launch in the US. The safety assessor asks for an ISO 11930 report for the EU file. The US distributor asks for USP 51 in its supplier requirements. The brand orders ISO 11930 first, since the EU launch comes first, and orders USP 51 on the same formula when the US contract is signed. Both reports end up in the Product Information File.
Practical advice when comparing quotes
- Check that the standard and edition are written on the quote, for example ISO 11930:2019.
- Check that all five microorganisms and all sampling days are included.
- Ask whether the report is signed and acceptable for a CPSR.
- Ask how a repeat test would be priced.
Why labs and assessors sometimes disagree
Laboratories often offer the standard they know best, while assessors follow the guidance of the regulation and the customer. If the two do not match, the result may be questioned even though the science is sound. A one-line confirmation from your assessor before you order avoids this mismatch and the cost of a second test.
A note on edition and amendments
Standards change. ISO 11930 has a 2019 edition and was amended in 2022, and pharmacopoeia chapters are revised periodically. Always state the edition on your order and in your file, so that anyone reading the report knows exactly which version of the method was used.
Frequently asked questions
Is Ph. Eur. 5.1.3 accepted for cosmetics?
Some safety assessors accept it, but ISO 11930 is the usual reference. Confirm with your assessor first.
Do both standards take the same time?
Yes, both use a 28-day incubation.
Which standard is cheaper?
The price depends on the laboratory and product, not on a standard being inherently cheaper.
Key takeaways
- ISO 11930 is the cosmetics standard; Ph. Eur. 5.1.3 comes from pharmacopoeia and USP 51 from the US.
- All use five microorganisms, 28 days and criteria A and B.
- For an EU cosmetic, ISO 11930 is the safest choice.
- Ask your assessor before ordering and state the standard on the order.