CPSR Part B Explained: Inside the Cosmetic Product Safety Assessment

If Part A is the evidence file, Part B is the verdict. It is the section of a Cosmetic Product Safety Report where a qualified safety assessor weighs up all the data and formally concludes whether your product is safe to sell. Part B is the legally meaningful sign-off — the part an authority looks to first. This guide explains what it contains, how the safety calculation works, and what it really means when your assessor passes, conditions, or does not pass your product.

Part B is defined by Annex I, Part B of Regulation (EC) No 1223/2009, retained in UK law after Brexit. It is titled Cosmetic Product Safety Assessment, and unlike Part A — which is largely data you supply — Part B is the assessor's professional reasoning and decision. It is where scientific judgement, rather than raw information, takes over.

What is Part B of a CPSR?

Part B is the conclusion of the safety report. The assessor takes everything assembled in Part A — composition, exposure, toxicological data — and reasons toward a documented judgement on whether the product can be placed on the market safely, and under what conditions. It is signed and dated by the assessor, who must be appropriately qualified. Without a completed, signed Part B, you do not have a valid CPSR, no matter how thorough your data is.

In practice, Part B is what gives the whole exercise its legal force. An authority reviewing your file will look to the conclusion and the signature first, then check that the reasoning behind it is sound and that the warnings it requires actually appear on your label.

The four components of Part B

1. Assessment conclusion

A clear statement on the safety of the product: whether it is safe for human health when used under normal and reasonably foreseeable conditions. This is the headline finding of the entire report, and everything else in Part B exists to justify it.

2. Labelled warnings and instructions for use

The assessment often identifies precautions that must appear on the packaging — for example “avoid contact with eyes”, “for external use only”, a maximum usage frequency, or a warning tied to a specific ingredient or concentration. These warnings are not optional marketing copy; they are part of your legal labelling, flowing directly from the safety assessment. If your label and your Part B disagree, your label is wrong.

3. Reasoning

The scientific justification that links the data in Part A to the conclusion. This is where the assessor explains *why* the product is safe, including the Margin of Safety calculations for ingredients of concern and any read-across or weight-of-evidence reasoning used. Good reasoning is what makes a CPSR defensible if it is ever scrutinised.

4. Assessor's credentials and approval

Proof that the person signing holds the required qualifications, plus their formal, signed approval. This is what gives Part B its legal standing — and why who signs your CPSR matters so much. An unqualified signature can invalidate an otherwise sound report.

Key point: the warnings produced in Part B must match what appears on your label. A mismatch between your safety assessment and your packaging is a common compliance failure that authorities and marketplaces do spot.

The Margin of Safety, explained simply

The heart of Part B's reasoning is the Margin of Safety (MoS). You do not need to perform this calculation yourself, but understanding it helps you see what your assessor is doing. In plain terms, the MoS compares the dose of an ingredient known to be safe in studies against the dose a person actually receives from your product.

It rests on two figures. The NOAEL (No Observed Adverse Effect Level) is the highest dose of a substance shown to cause no harmful effect in testing. The SED (Systemic Exposure Dose) is how much of that substance a real user absorbs from your product, based on the exposure data from Part A. The Margin of Safety is essentially the NOAEL divided by the SED — in other words, how many times larger the safe dose is than the real-world dose.

As a general benchmark, a Margin of Safety of 100 or more is considered acceptable for a given substance. That factor of 100 builds in a safety buffer to account for differences between test conditions and real people — broadly, a factor of 10 for differences between species and another factor of 10 for differences between individuals. If the margin falls below that threshold, the assessor may require a lower concentration of the ingredient, a usage restriction, or reformulation before the product can pass.

What label warnings come from Part B

One practical output of Part B that brand owners often underestimate is the set of label warnings and instructions. Depending on your formula, the assessment might require statements such as a usage limit, an age restriction, a rinse-off instruction, or a specific caution for products used near the eyes. Because these flow from the safety assessment, you cannot finalise your packaging artwork with complete confidence until Part B is done. Printing labels first and assessing later is a classic and avoidable mistake.

Pass, conditions, or reformulate

A Part B assessment does not simply return “yes” or “no”. There are usually three possible outcomes:

• Safe as formulated — the product passes and can be placed on the market, possibly with standard label warnings.
• Safe with conditions — the product passes but only with specific warnings, usage limits, or a restriction on who should use it (for example, not for children under three).
• Not safe as formulated — one or more ingredients exceed safe limits or fall below an acceptable Margin of Safety. The assessor will flag what needs to change, and you reformulate and resubmit.

This is why it pays to have your formula reviewed early. Discovering a problem at the assessment stage is far cheaper than discovering it after you have printed labels, ordered packaging and built stock. A quick pre-assessment review can save a great deal of money and frustration.

Who signs Part B?

Part B must be signed by a qualified safety assessor — typically someone holding a degree in pharmacy, toxicology, medicine or a related scientific discipline, with cosmetic safety training. The signature is what makes the document legally valid. We cover the exact requirements, and how to check an assessor is genuinely qualified, in our guide to who can sign a CPSR.

A simple Margin of Safety example

A simplified illustration shows how the pieces fit together. Suppose an ingredient has a NOAEL of 50 mg per kg of body weight per day from toxicological studies. The assessor works out, from your formula percentage and the exposure data in Part A, that a typical user actually absorbs around 0.2 mg per kg per day — that figure is the SED. Dividing the NOAEL by the SED gives a Margin of Safety of 250. Because that comfortably exceeds the benchmark of 100, the ingredient is considered safe at the level used in your product.

Now imagine the same ingredient used at a much higher concentration, pushing the SED up to 1 mg per kg per day. The margin falls to 50 — below the threshold — and the assessor would ask you to reduce the concentration or restrict how the product is used. The numbers here are purely illustrative, but they show why the exposure data you provide in Part A has such a direct effect on whether your product passes. Small formulation changes can move a product from comfortably safe to needing a rethink.

How long does Part B take?

Once your Part A data is complete and accurate, the assessment itself is usually a matter of days to a couple of weeks, depending on the complexity of the formula and the assessor's workload. The longer waits in the process almost always come from missing data or outstanding laboratory tests — not the reasoning in Part B. This is the practical reason we stress getting your documentation right first: the verdict is rarely the bottleneck, but the evidence behind it can be.

Keeping Part B valid over time

A signed Part B reflects your product and the rules as they stood on the day it was signed. Neither of those is fixed forever. If you change your formulation — swap a preservative, adjust an active, alter a fragrance — the original assessment no longer describes what you are selling, and it needs revisiting. Equally, ingredient restrictions are updated regularly, and a substance that was acceptable at a given level may later be limited or banned. A responsible approach treats Part B as a living conclusion that is reviewed when your product or the regulations move, not a certificate you file once and forget. Building in periodic review is far cheaper than discovering an out-of-date assessment during an enforcement check or a marketplace audit.

Frequently asked questions

What is CPSR Part B?

Part B is the Cosmetic Product Safety Assessment — the section where a qualified assessor concludes whether the product is safe, sets out required label warnings, gives the scientific reasoning, and signs the report.

What is the Margin of Safety in a CPSR?

The Margin of Safety (MoS) compares the no-effect dose of an ingredient (NOAEL) with the dose a user actually absorbs (SED). A MoS of 100 or more is generally considered acceptable.

What happens if my product fails Part B?

The assessor flags which ingredients exceed safe limits or fall below an acceptable margin, and you reformulate and resubmit. Catching this early avoids wasted spend on labels and stock.

Are the warnings in Part B mandatory on my label?

Yes. Warnings and instructions identified in Part B are part of your legal labelling and must appear on the product. A mismatch between Part B and your label is a common compliance failure.

Who is allowed to sign Part B?

Only a qualified safety assessor — typically holding a degree in pharmacy, toxicology, medicine or a related science with cosmetic safety training. Their signature gives the CPSR its legal validity.

Reference: Annex I, Part B of Regulation (EC) No 1223/2009 (EUR-Lex), retained in UK law; SCCS Notes of Guidance on Margin of Safety methodology. General information only, not product-specific advice.