The “12M” on your cosmetics means the product is designed to stay safe and effective for 12 months after you first open it. The “M” stands for months, and the number tells you how many. You’ll usually find this printed inside or next to a small icon of an open jar, which is formally called the Period After Opening (PAO) symbol.
How the PAO Symbol Works
The open jar icon with a number like 6M, 12M, or 24M is required on cosmetics sold in the European Union, but most global brands use it regardless of where they sell. The symbol is intentionally language-neutral: “M” is the initial for “month” not only in English but also in Latin and many other European languages, so it works across markets without translation.
The number refers specifically to the time after opening, not from the date of manufacture or purchase. A moisturizer sitting sealed on a shelf for a year hasn’t started its PAO countdown yet. That clock begins the first time air, fingers, or applicators contact the product inside.
PAO vs. Expiration Dates
These are two different systems. An expiration date applies to unopened products and tells you how long the sealed item remains stable. The PAO symbol only kicks in once you break the seal. Under EU cosmetic regulations, products with an unopened shelf life of 30 months or more get a PAO symbol instead of a printed expiration date. Products that expire in under 30 months get a traditional expiration date instead.
In the United States, the FDA does not require cosmetics to carry expiration dates or PAO symbols at all. That means many U.S. products rely on the PAO icon voluntarily, and some carry no date guidance whatsoever. If your product has no symbol, you’ll need to rely on general guidelines and your own senses to judge whether it’s still good.
Why the Timeframe Matters
Every time you open a product, you introduce air, moisture, and bacteria from your skin or applicators. Cosmetics contain preservatives to fight microbial growth, but those preservatives break down over time, especially with repeated exposure to air and heat. Once they lose effectiveness, bacteria and fungi can multiply inside the product.
Research on used mascaras illustrates how quickly this happens. A study analyzing 40 mascara samples found Staphylococcus aureus, a bacterium that causes skin and eye infections, in 79% of them. Pseudomonas aeruginosa, which can cause serious eye infections, appeared in 13%. Nearly all participants in the study reported using makeup past its expiration period, and over 70% had expired products in active use on the day they were surveyed.
Typical PAO by Product Type
Not all cosmetics get the same timeframe. Water-based and liquid products spoil faster because moisture is where bacteria thrive. Dry, pressed products last much longer.
- Mascara: 3 to 6 months. This is the shortest of any common cosmetic because the wand repeatedly transfers bacteria between your lashes and the tube.
- Liquid foundation and concealer: 6 to 12 months. The “12M” you’re seeing likely appears on one of these.
- Powder eyeshadow and blush: Up to 24 months, assuming you apply with clean brushes rather than fingertips.
- Lipstick and lip gloss: 12 to 18 months.
- Skincare (serums, moisturizers): 6 to 12 months for most formulas, though products with active ingredients like vitamin C can degrade faster.
How to Tell a Product Has Gone Bad
The PAO date is a guideline, not a hard cutoff. Sometimes products go bad before their PAO period ends, particularly if stored in a hot bathroom or contaminated by dirty hands. Other times a well-stored powder might last beyond its printed date. Your senses are a reliable backup system.
Color shifts are one of the earliest signs. A beige foundation that looks slightly orange has started to oxidize and break down. Smell is another strong indicator, especially for foundations and mascaras. If a product smells different from when you bought it, or has developed any sour or chemical odor, it’s done. Texture changes matter too: foundation separating into layers, mascara drying out on the wand, or moisturizer becoming grainy all signal degradation. Visible mold, which can appear as small spots or fuzzy patches inside the container, means the product should be discarded immediately.
Tracking Your Opening Date
The biggest practical challenge with PAO symbols is that nobody remembers exactly when they opened something. A simple fix is writing the date on the bottom of the container with a permanent marker the first time you use it. Some people use a small sticker or a note in their phone. For a product marked 12M that you opened in January, you’d know to replace it by the following January.
Storage also extends or shortens the effective life of your products. Keeping cosmetics in a cool, dry place away from direct sunlight helps preservatives last longer. Bathroom counters near showers expose products to repeated heat and humidity, which accelerates preservative breakdown and bacterial growth. Keeping lids tightly closed and using clean applicators instead of fingers reduces the amount of bacteria introduced with each use.