A cosmetic pack carries two clocks: the clock that runs from the day it is made, & the clock that starts the day the customer opens it. Most brands brief the first & forget the second, then discover that the open-jar mark the law expects is missing from the artwork. The omission is a labelling finding, not a formulation fault, & it is the easiest one for a market to catch at the border.
This article sets out the period-after-opening mark, the date of minimum durability, & the batch code, & explains which applies when & what a brand may & may not state on the pack. It is written for the brand owner or the artwork lead who has to lock a label before the print, not for the regulator who will read it. Read it before the dieline is cut, because the date block changes the layout & the file behind it.
Why opening changes the clock on a cosmetic pack
A sealed cosmetic is stable under the conditions the shelf-life study assumed. The moment the customer opens it, air, fingers & a used finger introduce microbes & oxygen that the sealed pack never saw, & the product ages faster from that point than the sealed clock suggests. The period-after-opening figure exists to tell the customer how long the open product is good for, separate from the sealed date.
The two clocks answer different questions. The expiry or minimum-durability date says how long the sealed pack is good for; the PAO says how long the opened pack is good for. A brand that prints one & assumes it covers the other has left a half of the story off the label, & the missing half is usually the one the rule requires.
The practical point is that the open-jar figure is a separate assessment built on the preservative system & the use pattern, not a fraction of the sealed life. A product that is stable for three years sealed may only be safe for six months once opened, & the brand should hold the basis for the opened number rather than guessing it.
The period-after-opening mark & what it means
The period-after-opening mark is the open-jar symbol followed by a number of months, placed on the pack for products with a shelf life longer than the threshold the market sets. It tells the customer that once opened, the product should be used within that many months. It is a use-life signal, not a safety guarantee, & it appears on the pack rather than on the sealed date.
The figure is set from the formulation, the preservative challenge & the packaging, & it should reflect the worst realistic use. A product used with wet hands from a wide jar needs a shorter PAO than the same formula in a pump, because the exposure differs, & the pack choice is part of the number, not separate from it.
What a brand cannot do is print a PAO it has not supported. The figure should rest on a preservative efficacy test & the stability data, & a number chosen for convenience invites a finding if the product fails within the stated window. The mark is a promise the brand can be asked to defend, & the file behind it should exist before the print.
The date of minimum durability & when it applies
The date of minimum durability, often shown as a best-before or a production-plus-shelf-life date, applies to the sealed product. In most systems it is required where the product's shelf life from manufacture is below the threshold the local rule sets, & it tells the customer the sealed pack should be used by that date. Above the threshold, the PAO often substitutes for it.
The exact threshold & the format vary by market, so the brand should confirm which rule applies rather than assume a single global practice. A date format that satisfies one market can be read as missing by another, & the artwork should be set per destination or kept neutral enough to satisfy all.
The date is only as good as the stability data behind it. A brand that prints a date without a study is stating a shelf life it cannot support, & a regulator or a retailer may ask for the basis. The date & the study should be built together, with the study setting the date rather than the date leading the study.
Batch code: the third piece the label needs
The batch code ties the pack to the manufacturing record, & it is the piece that lets a question about a specific unit be answered months later. A PAO or a date without a batch code is a half measure, because the brand cannot trace what was made when if a complaint arrives. The code is the link between the label & the factory file, & its role in traceability is set out in our batch code article.
The code should be legible, durable & present on the primary pack or the outer pack, depending on the market, & it should match the record the factory holds. A code that rubs off or that does not match the batch record defeats the purpose, & the brand should specify the method as part of the label brief.
The batch code also supports the date. Where a product carries a production date rather than a fixed expiry, the code is what lets the customer or the authority work back to when it was made, & the two should be consistent. A mismatch between code & date is the kind of detail an audit catches first.
What the two dates do not let a brand claim
A PAO or an expiry date is a stability statement, not a performance claim, & it does not let the brand say the product does anything for the skin, the hair or any body function. The date block answers how long is it good for, not what does it do, & the two should not be blurred on the pack or in the copy.
The brand also cannot use a long PAO as evidence of a benefit. A twelve-month open life is a microbial & a stability result, not a quality promise, & wording that implies the product is better because it lasts longer crosses into a claim the local rule may challenge. The date is factual; the praise around it should be kept separate.
The safer habit is to print the marks as required & to keep the marketing copy on a different part of the label, with its own substantiation. A factory can confirm the date block the pack needs; it cannot confirm the claim copy, & a label that mixes the two is the one most likely to be queried after launch.
Storage conditions & the basis for the number
Both the PAO & the expiry rest on storage conditions the study assumed. A product tested at normal room temperature cannot be promised for a hot warehouse, & the label should carry any storage note the basis requires, such as keep away from heat or keep the cap closed. The note is part of the number, not a decoration.
The basis is a stability study, often supported by a preservative efficacy test for the opened figure, & the brand should hold both before printing. A PAO set without a challenge test is an assumption, & an assumption is what fails a retailer's documentation request. The study is the asset the date depends on.
The brand should also confirm the conditions of transport, because a product that sat in heat during shipping may not match the sealed clock by the time it reaches the shelf. The transport note is a separate line in the file, & the brand should hold it rather than assume the sealed date survives every lane.
Market differences a brand should map
The marking rules differ by destination. Some markets require the PAO above a certain shelf-life threshold; some require a date of minimum durability below it; some require both in specific forms. The brand should map the rule per market rather than print one global label, because a single label rarely satisfies all.
The format of the date & the symbol also varies. The open-jar symbol is widely used, but the surrounding text, the language & the placement are set locally, & a symbol without the required local text can be read as incomplete. The artwork should be set per destination or kept neutral enough to satisfy all.
The documentation behind the marks should travel with the product. A brand that prints a PAO in one market & ships the same pack elsewhere should confirm the basis is accepted where it sells, because a mark printed without local acceptance is a finding waiting at the border. The mapping is part of the launch plan, not an afterthought.
Single-use & sachet packs: the exceptions
Some packs are exempt from the PAO because they are not intended to be opened & used over time. Single-dose sachets, samples & other packs that are used at once fall outside the open-jar logic, because there is no opened period to mark. The brand should confirm the exemption per market rather than assume it, because the line is drawn differently by destination.
The expiry or minimum-durability date can still apply to these packs, because they are sealed goods with a shelf life, even if the PAO does not. A sachet that is stable for eighteen months sealed may still need a date, & the brand should not read the PAO exemption as a pass on the date.
The practical move is to brief the pack type with the market list, so the factory & the label lead agree which marks apply to which format. A brand that regards every pack the same misses the exemptions & over-labels some formats, which is a cost & a clutter the brand does not need.
Documentation behind a defensible date
Behind every PAO & every date sits a file: the stability study, the preservative efficacy test, the specification sheet, the batch record & the retention sample. These are the items a regulator or a retailer will request if the date is questioned, & they should be ready, not reconstructed under pressure.
The retention sample is what ties the date to a physical product. A sample of the batch the date covered lets the brand answer a later question about what was actually made, & it supports the open-jar figure as the product ages. Without it, the date is an opinion about a formula that may no longer match the goods.
The brand should keep the file for the period the applicable rule requires, & should name the owner, because a file with no owner drifts & a question asked two years later finds nothing. The discipline is the same one a quality agreement imposes on the factory, applied to the shelf-life file.
PAO, expiry & batch code at a glance
The table below sets the three label elements against the question each answers, with the basis each rests on. It is a relative summary from common practice, not a fixed legal rule, & the exact threshold & format should be confirmed for each market the product is sold in.
| Label element | Question it answers | Basis it rests on | Common failure |
|---|---|---|---|
| Period after opening | How long once opened | Preservative efficacy & stability | Symbol shown with no verified number |
| Date of minimum durability | How long sealed | Stability study | Study run on a different pack |
| Batch code | Which batch was made | Manufacturing record | Code too small to read |
| Open-jar symbol | Visual PAO marker | Local marking rule | Symbol only, no months stated |
| Storage note | Under what conditions | Study assumptions | Copied from another product |
| Production date | When it was made | Batch record & code | Confused with the expiry date |
| Exemption status | Whether PAO applies | Pack type & market | Exemption assumed without a check |
| Language & placement | How it is shown | Local text rule | Text in the wrong language |
The rows are a starting point, & the order reflects the sequence a label lead usually works through. A brand that sets the three elements from the study rather than from habit tends to print a label that survives an audit, which is the outcome that protects the listing.
What to put in the brief
Brief the label as a compliance item with the file behind it, so the factory supplies the stability & the batch data while the artwork is still a draft rather than after the cylinders are cut. Name the markets, the pack type & the format, & the label can be set per destination before the print.
- The markets the product will be sold in, & any that are planned within two years.
- The pack type, & whether it is a long-use or a single-dose format.
- The stability data, & the preservative efficacy test for the PAO.
- The shelf life the brand intends to state, & the basis for it.
- The batch code method, & where it sits on the pack.
- The storage note the basis requires, & how it is shown.
- The label copy obligations, separate from the date block.
- The documentation the brand will hold, & who owns it.
Then confirm the exemption per market, because a single global label rarely satisfies all destinations & the over-label is a cost the brand does not need. The dieline work that locks the date block is covered in our label dieline guide, & the brief is what turns a date question into a printable pack.
Where our capability fits
We supply the technical half of the date block: the stability study summary, the preservative efficacy result, the specification sheet, the batch record & the retention sample, all built so the brand can set a PAO & a date with a basis rather than a guess. We confirm the batch code method with the label lead at the artwork stage, so the code matches the record the factory holds.
We work with brands on private label (your brand on a proven base), OEM/ODM contract manufacturing & full custom formula development, & the date block is specified as part of the product rather than as a late addition. Our lines include custom cosmetic softgel capsules, a firming face cream & hyaluronic acid serum capsules, all produced with the same batch record & retention discipline a shelf-life file depends on.
Tell us the markets you sell into & the pack type you are using, & we will come back with the stability & batch data your label needs, & the PAO we would support for the format. Start at our inquiry page, email capsulebiotech@163.com, or message the right team on WhatsApp: Capsule Series (capsules only) +86 158-7655-5319, Cosmetics Series (serum, hair care, body care, fragrance) +86 158-7655-5319.
General manufacturing information, not regulatory or legal advice. Period-after-opening marks, minimum-durability dates, batch-code rules & labelling formats vary by market & by product, & the applicable requirements should be confirmed for each destination before a product is placed on sale.