The Period After Opening Symbol and When You Need It

The little open-jar icon with a number and an "M" inside it confuses more makers than almost any other label element, mostly because people assume it's mandatory on everything. It isn't. It's tied to a specific durability logic, and once you understand that logic the question of whether you need it answers itself.

What the symbol actually represents

The Period After Opening symbol, that open-jar icon with something like "12M" or "24M" inside it, tells a consumer how long a product remains safe and effective to use after it's first opened, not from the date of manufacture. It exists because a lot of cosmetics degrade or become more susceptible to contamination once the seal is broken and air, fingers, and applicators start interacting with the product.

This is fundamentally different from a fixed best-before or expiry date, which counts from the manufacturing date regardless of when, or whether, the product gets opened.

When you use PAO instead of a fixed date

The general logic in EU cosmetics regulation is that products expected to remain stable for a long period, generally considered to be beyond a certain minimum durability, use a PAO symbol rather than a fixed expiry date, because the more meaningful risk window starts at first use, not at manufacture. A face cream with a long shelf life sitting unopened in a drawer isn't really the concern. The concern is what happens to it after someone's been dipping fingers into the jar for a year.

Products with a shorter overall durability, typically under the threshold where PAO logic applies, instead get a fixed date, often expressed as "best used by" alongside a date, sometimes paired with the batch code.

The two systems aren't interchangeable, and mixing them up is a common label mistake

A common error is putting both a fixed expiry date and a PAO symbol on the same product without a clear reason, or using PAO on a product whose actual stability profile calls for a fixed date instead. Your stability testing data should be the thing that decides which system applies to your specific product, not habit or copying what a competing brand does.

If your product is genuinely long-lasting once sealed but degrades faster once opened (many creams, lotions, and oil-based products fall into this pattern), PAO is the right fit. If it's a product that's more sensitive to time regardless of whether it's been opened (some naturally preserved or minimally preserved formulas), a fixed date may be more appropriate.

What goes into deciding the number inside the symbol

The number of months in your PAO symbol, 6M, 12M, 24M, and so on, should come from actual stability data, ideally including how the product performs once opened and exposed to normal use conditions, not a number picked because it looks reassuring. This ties directly back to your stability testing program. If you haven't tested how your product holds up after opening specifically, don't guess at a PAO number.

Where this fits in your EU notification

The Cosmetic Product Safety Report that your safety assessor signs off on, part of the Product Information File you keep as the Responsible Person, should include the reasoning behind your shelf-life and PAO decisions. This isn't just a labeling nicety; it's meant to be backed by the same safety and stability reasoning that supports the rest of your product's safety case when you notify through the CPNP portal.

A quick way to sanity check your own label

Ask yourself these questions before finalizing:

1. Does my stability data actually support the number I've put inside the PAO symbol, or did I estimate it?
2. Have I picked PAO or a fixed date based on which one fits my product's real degradation pattern, rather than copying a similar product?
3. If a regulator or Responsible Person asked me to justify this number tomorrow, could I point to actual test data?

Getting this right up front avoids relabeling costs later, and it's a small but real part of building a Product Information File that would hold up under review. If you're also managing the ingredient side of your EU filing, matching everything to INCI names and screening for restricted substances is the kind of groundwork Cosmetic Comply is expanding into alongside its current Canadian notification service.