Shelf Life or Period After Opening: Which Goes on Your Label

A maker asked us recently whether their moisturizer needed "the expiry date thing or the jar thing." Both, as it turns out, or neither, or one but not the other, depending entirely on what your stability data actually shows. These are two different pieces of information answering two different questions, and it's worth being precise about which one your product needs.

Two questions, not one

The closed-container shelf life answers: how long does this product remain safe and effective while sealed, untouched, before the customer ever opens it? That's the number tied to an expiry date or a "best used by" statement, and it comes from real stability testing under storage conditions you can defend if anyone ever asks.

The Period After Opening, shown as the little open-jar icon with a number like "12M" or "6M" inside it, answers a completely different question: once air, fingers, and daily use start interacting with the product, how long does it stay in good condition? This is about what happens after the seal is broken, not before.

A product can have excellent closed-container stability and a short PAO, or the reverse. They're not proxies for each other.

When you need which

Not every product needs a PAO symbol. If your stability and challenge testing shows the product is stable indefinitely once opened, or if the packaging format means there's essentially no exposure risk (a pump that never lets air or fingers touch the product, for instance, or a single-use sachet), a PAO symbol may not apply. In those cases the closed shelf life or expiry date does the labeling work on its own.

Conversely, some products genuinely don't need a fixed expiry date if your data supports long-term closed stability, but they still need a PAO because once opened, contamination risk or ingredient degradation kicks in faster than the shelf life alone would suggest.

A rough way to think about it:

Situation	Likely need
Anhydrous product, no water activity, sealed tube	PAO possibly, expiry maybe not required
Water-based emulsion in a jar, opened repeatedly	Both PAO and attention to closed shelf life
Single-use or unit-dose packaging	Neither, or shelf life only
Pump or airless dispenser with minimal air exposure	Depends on your stability data, could be either

The answer always comes back to your actual testing, not a rule of thumb copied from another brand's label.

Where the numbers actually come from

Neither number is a guess or an industry default you're allowed to borrow from a similar product. Both should trace back to stability testing you commissioned or performed, ideally supported by a preservative efficacy or challenge test for water-containing products. If you changed your preservative system, your fragrance load, or your packaging material, your old PAO number may no longer be valid, even if nothing else about the formula changed. Packaging matters here more than people expect: a jar that gets fingers dipped into it daily degrades differently than a pump that keeps the product sealed from air between uses.

If you don't have this data yet, that's a normal place to be early in product development, but it means you shouldn't be printing a PAO symbol with a number you pulled from a similar product on the market. That number is a specific claim about your formula in your packaging, and it needs to be backed by your own data or a lab's.

What goes wrong when these get confused

The most common mistake is treating the PAO symbol as decorative, something every "professional-looking" cosmetic label should have regardless of whether the data supports it. Makers slap a 12M jar icon on a product because it looks credible, without ever running a test that would tell them whether 12 months is remotely accurate. If a regulator or a customer complaint ever traces back to a product that degraded well before its printed PAO, that mismatch between the label claim and reality is exactly the kind of thing that draws scrutiny.

The second common mistake is confusing the two when reporting to a regulator. On a Health Canada Cosmetic Notification Form, what matters is your ingredient list and concentrations, not your PAO icon, but your broader safety and stability documentation should be internally consistent with whatever you're printing on the package. If your file says one thing and your label says another, that's a discrepancy worth fixing before it's ever asked about.

Get your own stability and PAO testing done first, then let the label follow the data. Cosmetic Comply doesn't run stability testing itself, but when you're mapping out your ingredient list and concentrations for a Canadian notification, having your documentation organized in one place makes it much easier to keep your label claims and your filing consistent with each other.