The Period After Opening Symbol on Cosmetic Labels

That little open-jar icon with a number and a letter inside, something like 12M or 24M, shows up on nearly every jar of moisturizer you own. It's called the Period After Opening symbol, PAO for short, and it's telling you something different from an expiry date. It's answering the question: once air and your fingers start getting into this product, how long is it still good?

PAO versus expiry date

An expiry date is about the unopened product sitting sealed on a shelf. It reflects how the formula holds up under whatever storage conditions the manufacturer tested, assuming the seal is never broken.

The PAO symbol reflects a completely different exposure. Once a jar is opened, air, light, and repeated contact with fingers or applicators introduce oxidation and microbial risk that a sealed container never faces. A cream that would technically remain stable for three years sealed might only be recommended for use within 12 months once it's opened, because that's the window where the preservative system and the formula's stability have actually been evaluated for real-world, post-opening use.

When you need one and when you don't

The PAO symbol is most relevant for jar and pot packaging, tubs of body butter, cream cleansers scooped out with fingers, that sort of thing, where the product is exposed to air and contamination repeatedly over its use life.

Products in sealed, single-use, or minimally exposed packaging often don't carry a PAO symbol at all:

• Single-use sachets or samples, since there's no "after opening" period to track
• Products with a shelf life under 30 months where the manufacturer has determined the unopened expiry is the more meaningful date
• Pump or airless dispenser packaging, in some cases, since the formula has much less air exposure than an open jar

Whether a PAO symbol is required or just a good practice depends on the market and the specific regulation you're selling under, so this is a genuine case where checking your target market's current labeling rules directly is worth the ten minutes, since practices vary and this article isn't a substitute for that check.

How the number gets decided

The PAO period isn't a guess pulled from industry convention. It's meant to be grounded in stability testing that simulates repeated opening, exposure to air, and typical handling over time, then observing how the formula, its preservative system, its scent, and its texture hold up. A well-preserved facial oil in a dropper bottle might earn a 12M rating. A water-heavy cream in a wide-mouth jar with weaker preservation might only support 6M.

If you're a smaller maker without access to formal stability testing, a few things still help you make a defensible, honest estimate:

• Look at how similar formulas from ingredient suppliers or reference formulations are rated
• Consider your preservative system's known effective range and whether it's rated for jar-style repeated exposure
• Err conservative. A shorter PAO period that undersells your product's real shelf life is a much smaller problem than an optimistic one that isn't backed by anything

What goes wrong when it's ignored

The most common mistake I see from smaller cosmetic brands is copying a PAO symbol from a similar product's label without actually knowing whether their own formula supports that period. A 24M symbol slapped on a product with a much weaker preservative system isn't just inaccurate, it's a real safety claim you're making about how long a consumer can keep using a product exposed to air and bacteria.

The second common mistake is skipping the PAO entirely on a jar product because nobody thought to test for it, then discovering during a labeling review that it's expected for that packaging format in your market.

A practical starting point

If you're developing a new jar or pot product and don't have in-house stability data yet, talk to your preservative supplier. Many can point you toward typical PAO ranges for formulas using their system at your usage rate, which gives you a reasonable, defensible starting estimate rather than a guess.

And when you're pulling together the rest of your label, the PAO symbol is just one piece next to your ingredient declaration, allergen disclosures, and any claims you're making. Cosmetic Comply's filing process walks through your full ingredient list and formula details as part of getting your CNF in order, which is a natural moment to double check that your labeling, PAO included, actually matches what you're telling the regulator about the product.