Turn over almost any tube of mascara, jar of moisturizer, or lipstick bullet and you will find a small illustration of an open cosmetic pot with a number and the letter M inside it. 6M. 12M. 24M.
Most people assume it is an expiration date. It is not. It is the period after opening, and the difference between those two things is where nearly every beauty product goes wrong.
What "period after opening" actually means
The period after opening, usually shortened to PAO, is the manufacturer's statement of how long a product stays safe and effective once the seal is broken and air, fingers, and bacteria get in.
It is defined in EU Regulation 1223/2009, which requires cosmetics to carry a date of minimum durability. Products that stay stable for more than 30 months are exempt from printing that date. Instead, the regulation says they must show "the period of time after opening for which the product is safe and can be used without any harm to the consumer," using the open jar symbol from Annex VII of the regulation, followed by the number of months.
So the open jar is not a marker of decline. It is the opposite. It appears on products stable enough that the brand did not have to print an expiration date at all.
How to read the PAO symbol
The number is months. The M is months. That is the whole code.
- 6M means six months of safe use after you open it
- 12M means twelve months
- 24M means two years
The clock does not start at manufacture. It does not start at purchase. It starts the moment you break the seal. A 12M serum bought in January and opened in June expires in June of the following year, not January.
The catch nobody mentions
The PAO symbol assumes you know when you opened the product.
That is the entire premise of the system, and it is the part that fails in every bathroom in the country. The packaging tells you how many months you have. It has no way of telling you how many you have already used. Unless you wrote it down, 12M is not information. It is a math problem missing a number.
This is why so many people carry a vague sense that a product is "probably still fine." Without an open date, probably is all anyone has.
Why you may not see the symbol at all in the US
The PAO requirement is European. In the United States, there is no equivalent rule. The FDA states plainly that "there are no U.S. laws or regulations that require cosmetics to have specific shelf lives or have expiration dates on their labels."
Many brands print the symbol anyway, because they sell into the EU and use one label worldwide. But a US-only brand can legally sell you a product with no durability information whatsoever. The FDA puts the responsibility on the consumer, noting that how safely you use cosmetics depends in part on your own practices.
The one common exception is sunscreen, which the FDA regulates as an over-the-counter drug rather than a cosmetic. Sunscreen carries a real expiration date.
Where this matters most: the eye area
The FDA is direct about this. "Eye-area cosmetics tend to have shorter shelf lives than other products, which may cause eye infections that can be serious."
The reason is mechanical. A mascara wand travels from the lash line into a warm, dark, enclosed tube, several times a week, for months. Every pass brings back skin flora, tear film, and whatever was on the lashes. The tube is a small incubator with a fresh inoculation on a regular schedule. We covered that cycle in detail in the three-month rule for mascara.
Research bears this out. A 2019 study by Dr. Amreen Bashir and Professor Peter Lambert at Aston University, published in the Journal of Applied Microbiology, tested used lipsticks, lip glosses, eyeliners, mascaras, and beauty blenders. Between 79 and 90 percent of all used products were contaminated with bacteria, including Staphylococcus aureus, Escherichia coli, and Citrobacter freundii. Beauty blenders were by far the worst, and 93 percent of them had never been cleaned. If you want the microbiology, we broke down what actually grows inside a used product.
For eye products, the FDA notes that manufacturers usually recommend discarding mascara two to four months after purchase. That is a shorter window than most PAO symbols suggest, and shorter than almost anyone actually observes.
Typical PAO windows by product
These are common manufacturer ranges. Always defer to the number printed on your specific product.
| Product | Typical PAO | Why |
|---|---|---|
| Mascara and liquid liner | 3M to 6M | The wand returns to the tube after touching the lash line every single use. |
| Cream and liquid eye shadow | 6M to 12M | Water content plus finger or applicator contact near the eye. |
| Powder eye shadow | 12M to 24M | Low water activity slows growth, but brushes still reintroduce bacteria. |
| Liquid foundation and concealer | 6M to 12M | Emulsions with water. Pump packaging holds up better than open jars. |
| Lipstick and lip liner | 12M to 24M | Waxy base is less hospitable, but the applicator touches the mouth. |
| Lip gloss | 6M to 12M | Doe-foot wand plus saliva contact each application. |
| Serums and moisturizers | 6M to 12M | Actives degrade and jars invite finger contact. |
| Sunscreen | Expiration date, not PAO | Regulated as an OTC drug in the US, so it carries a true expiration date. |
For a product-by-product breakdown of everything else on your vanity, see our full replacement guide.
How to make PAO usable in real life
The symbol only works if you close the loop it leaves open. Three habits do it:
1. Record the open date, not the purchase date. The month you break the seal is the only date that matters. Write it on the product itself, not in a note you will never open again.
2. Give eye products their own, shorter clock. Whatever the tube says, treat mascara and liquid liner as three-month products. The wand-to-lash-line-to-tube cycle is a category of risk the printed number does not distinguish.
3. Stop assessing by look and smell. Bacterial contamination is usually invisible. Preservative systems deplete quietly, long before anything separates, smells off, or changes color. By the time a product looks wrong, it has been wrong for a while.
The bottom line
The period after opening symbol is genuinely useful information. It is a manufacturer telling you exactly how long their preservative system is designed to hold. The failure is not in the number. It is in the gap between the number and your memory.
Close that gap and the symbol does its job. Leave it open and 12M means nothing at all.
The PAO symbol tells you how long. EyeVida replacement cues tell you when you started. Mark the month you opened it, and the math is already done.
Frequently asked questions
What does period after opening mean?
Period after opening, or PAO, is the number of months a cosmetic stays safe and effective after the seal is first broken. It is shown as an open jar symbol with a number and the letter M, such as 12M for twelve months.
Is the PAO symbol the same as an expiration date?
No. An expiration date is fixed and applies from manufacture. PAO starts when you open the product, so the same item can expire on completely different dates for two different people.
What does 12M mean on makeup?
It means the product is designed to remain safe for twelve months after you open it.
Is period after opening required in the United States?
No. The FDA does not require expiration dates or shelf lives on cosmetic labels. Many brands print the PAO symbol anyway because it is required in the European Union under Regulation 1223/2009 and they use one label globally.
What happens if I use a product past its PAO?
The preservative system may no longer control bacterial growth. Risk is highest for eye-area products, which the FDA notes can cause eye infections that may be serious. Speak with your eye doctor or dermatologist about any irritation or infection.
Sources
- Regulation (EC) No 1223/2009 on cosmetic products, Article 19(1)(c) and Annex VII.
- US Food and Drug Administration, Shelf Life and Expiration Dating of Cosmetics.
- Bashir A, Lambert P. Microbiological study of used cosmetic products: highlighting possible impact on consumer health. Journal of Applied Microbiology, 2019.
EyeVida stickers are an organizational tool, not a medical device, and are not intended to diagnose, treat, cure, or prevent any disease.