Cosmetic Product Safety Report PAO: How the CPSR Sets the Period After Opening

A brand asked us recently whether it could print 24M on a jar cream, because a competitor did. The honest answer was another question: what stability data do you hold? There was none, the challenge test had passed, and the assessor supported six months. Nothing about that exchange is unusual. The period after opening is the part of a cosmetic label most often chosen by looking at a competitor, and it is one of the parts most firmly grounded in evidence, because Article 19 of Regulation (EC) No 1223/2009 requires the durability information and the Cosmetic Product Safety Report has to support it. The UK regulation enforced through the Cosmetic Products Enforcement Regulations 2013 works the same way, and the methods come from the SCCS Notes of Guidance.

This article explains how the number is actually reached. It covers the two symbols and the thirty month rule that decides which one you print, the evidence ladder from no data to full stability and what period each rung supports, what stability testing and challenge testing each contribute, how packaging changes the answer by months, the product type ceilings that no amount of data can lift, what Part B says and why it binds you, a worked example of three versions of the same cream, a typical PAO table for reference, and what a consumer sees at the end of all this. If you have ever guessed a PAO, this is the conversation to have before the next print run.

Which symbol do I print, and why?

The rule turns on thirty months of unopened durability. If your product remains safe and fit for use for more than thirty months unopened under normal storage, you do not print a date; you print the open jar symbol with a number of months, which is the period after opening. If its durability is thirty months or less, you must print a date of minimum durability, shown as best before end or with the hourglass symbol, and you do not print a period after opening. One or the other, never both. The logic is that a long lived product's risk comes from opening and use, so the consumer needs to know how long after opening it stays good, while a short lived product's risk comes from time itself. Stable products such as anhydrous balms, oils and well preserved emulsions typically exceed thirty months and carry the symbol; products with sensitive actives or fragile systems often do not.

The evidence ladder: what each level of data supports

The ladder is the whole answer to why one brand prints 6M and another prints 24M on apparently similar products. It is not confidence or caution; it is what each of them can show.

What does stability testing actually contribute?

It tells the assessor whether the product still is what it was. Accelerated stability holds samples at elevated temperature, often with freeze and thaw cycles and light exposure, and checks appearance, colour, odour, viscosity, pH and, where relevant, active content at intervals; real time stability does the same at normal storage over the product's intended life. What the assessor is looking for is drift: an emulsion beginning to separate, a pH climbing out of the preservative's working range, an active degrading, a fragrance turning. These are recorded in Part A section 2 alongside the physical and chemical characteristics, and they are what justify a longer period after opening, because a product that has held its properties for twelve weeks at forty degrees is a product whose properties will hold on a bathroom shelf.

What does the challenge test contribute?

The preservative efficacy or challenge test inoculates the product with defined organisms and measures whether the preservative system reduces them over a set period, which models the contamination a consumer introduces with fingers, water and air. It is the evidence behind Part A section 3, the microbiological quality, and it is required for effectively every water based product. It also has a bearing on the period after opening in two ways: a system that passes strongly supports a longer period, and a system that passes marginally supports a shorter one. For anhydrous products used in wet environments, such as a sugar scrub kept in a shower, the assessor may ask for a water spiked variant of the test, because the product in the customer's jar is not the product that left the factory. Our article on what a CPSR costssets out where challenge and stability testing sit in a launch budget, and their turnaround is usually the longest item in it.

How much is packaging worth?

Months, sometimes six of them. A wide mouthed jar is opened with fingers, exposes the whole surface to air at every use, and accumulates whatever is on the user's hands; an airless pump or a tube keeps fingers out, limits oxygen and dispenses without back flow. Two products with the same formula and the same test results can therefore support different periods, and the assessor will say so explicitly. A spatula supplied with a jar, and directions to use it, help but do not equal a pump. Single use sachets remove the question. For anhydrous products the same logic applies to water rather than microbes: a tube keeps a shower scrub dry where a jar cannot. If you are choosing packaging and you want a longer period after opening, this is the cheapest lever you have, and it is decided long before the report is written.

The ceilings no evidence can lift

Some periods are capped by the use rather than the formula. Mascara and liquid eyeliner are held to three to six months because the applicator travels between the eye and the container repeatedly and eye infections are the risk being managed. Eye creams sit around six months for related reasons. Products for babies and for use on compromised skin are treated conservatively. Sunscreens are typically twelve months because the labelled protection is only supported within the tested period and degradation is invisible to the user. In each case a brand can hold immaculate stability data and still receive a shorter period after opening in Part B, and an assessor who ignores these ceilings is not doing the job. The ceilings exist because the period after opening is a safety statement rather than a quality one.

What does Part B say, and why does it bind you?

Part B states the conclusion and the conditions, and where a period after opening has been established it appears there, often tied to other conditions such as a storage instruction, a pH range or a packaging type. Once Part B sets it, it is a specification. Printing a longer period is a labelling breach and an unsupported claim, and it is one of the easier things for a Trading Standards officer to check, because the officer can ask for the report and compare it with the pack. It also matters commercially: an insurer looking at a reaction claim, or a marketplace compliance team reviewing a listing, will do the same comparison. If the period Part B supports is shorter than you want, the route is more evidence or different packaging, not a bigger number.

A worked example: three versions of one cream

A brand develops a hydrating cream and asks Spectra to assess three versions. Version one is in a 50 ml jar with no stability data and a passed challenge test; the assessor supports six months. Version two is the same formula in the same jar, with twelve weeks of accelerated stability showing stable pH, viscosity and appearance; the assessor supports twelve months. Version three is the same formula in an airless pump, with the same stability data and the same challenge test; the assessor supports twelve months and notes that real time data at twelve months would support eighteen. The brand launches version three, adds a real time study running alongside the first year of sales, and at the next addendum moves the pack to 18M with the data to back it. Same cream, three numbers, each of them defensible, and the difference between the first and the last is one stability study and a change of pack.

Typical periods after opening, for reference

What the consumer sees at the end of it

A symbol and a number, and the instruction to count months from the day the product was opened. What a consumer should also know, and what no symbol can convey, is that the period assumes normal storage and reasonable handling: a cream that has spent the summer on a sunny windowsill, a jar used with wet hands, or a pump bottle topped up with water has left the conditions the assessment covered. Any change in smell, colour, texture or performance means the product is finished regardless of the months remaining. That is not a defect in the system; it is the difference between an evidence based maximum and a guarantee, and it is the same distinction that runs through every conclusion in a Cosmetic Product Safety Report.

Myths we hear

• The PAO is a marketing choice. It is a conclusion in Part B based on evidence.
• Everyone prints 12M so we can too. Everyone who prints it should be able to produce the file behind it.
• The symbol and a best before date are interchangeable. One counts from opening, the other is a fixed date, and the thirty month rule decides which you print.
• Anhydrous products do not need a period. They do, driven by oxidation and by contamination in use.
• A longer PAO makes the product look better. An unsupported one makes the label unlawful.

What to do this week

• Check what period after opening each of your products carries and what evidence supports it. 
• Compare every pack against the Part B conditions in its report. 
• Book accelerated stability for any product where you want a longer period. 
• Consider a tube or airless pump for the next pack change. 
• Start a real time study alongside your first year of sales. 

The number on the jar is a small piece of the label with a whole file behind it, or behind it there is nothing. Spectra sets it from the evidence and tells you plainly what would let you print a longer one, and you can verify any report we sign before a retailer asks.

Related reading on the Spectra blog

•      Does one Cosmetic Product Safety Report cover every market?

•      Who should prepare your Cosmetic Product Safety Report?

•      What does a Cosmetic Product Safety Report cost in 2026?

•      All Spectra articles

Spectra services mentioned in this article

•      The Complete Compliance Pack: CPSR, PIF, SDS and SCPN or CPNP (£295)

•      CPSR services by product type

•      PIF services

•      UK and EU Responsible Person

•      UK SCPN Product Notification (from £15)

•      Contact Spectra

Official sources and legislation

•      Regulation (EC) No 1223/2009 on cosmetic products, Article 19 and Annex I

•      Cosmetic Products Enforcement Regulations 2013

•      Scientific Committee on Consumer Safety (SCCS), Notes of Guidance

Disclaimer: This article is general information, not legal advice. Regulations change and product decisions depend on your exact formulation, claims and market. Have your product assessed by a qualified professional before sale.