PAO: what it is and why it's important for your beauty routine

A direct impact on safety and efficacy

Every day, when we use a cosmetic, whether it's a cream, a serum, shampoo, lipstick, or even toothpaste, we primarily focus on performance and sensoriality.

But there's a piece of information we often forget to check that, in fact, has a direct impact on the safety and efficacy of the cosmetics we use: the PaO.

In this article, you will clearly discover what PaO is and why it should not be confused with the expiration date. It is therefore important to periodically declutter your cosmetics to protect your skin and hair.

What is PaO and why isn't it an expiry date?

PaO is an acronym for Period After Opening. It is a mandatory indication that tells us for how many months a cosmetic product can be safely used from the moment it is opened.

Unlike an expiry date, which is a fixed term (e.g., "use by"), PaO takes into account the product's stability after the packaging has been opened, air and light have begun to interact with the formula, and the user has started to handle it.

Expiration and validity: efficacy and safety

Almost no one knows this, but according to the current European Cosmetics Regulation (Reg 1223/2009 CE), cosmetic products should have a so-called validity date, and not an expiration date, stamped on the packaging.

What is the difference between the two?
Expiration is a pharmaceutical concept, after which the product cannot be used, while validity, which is a cosmetic concept, is the date by which the product maintains its efficacy characteristics.

However, the aforementioned regulation stipulates that, if the product's efficacy is maintained for at least thirty months, the indication of the validity date is no longer mandatory. Obviously, almost all cosmetic products are formulated in such a way that this minimum validity requirement is met.
The same regulation stipulates that, in this case, the consumer must still be informed about the time frame within which the cosmetic maintains its safety characteristics for human health. And this is where the PaO (Period after Opening) becomes mandatory, representing the number of months after the product has been opened during which, under normal storage conditions, the product can continue to be considered safe.

Why PaO is needed and why cosmetic decluttering is important

PaO exists to ensure that the product maintains efficacy and microbiological safety for as long as we use it. After the indicated period, we can no longer be certain that the formula is stable or that there is no contamination from bacteria, molds, or fungi.

This is why PaO should not be ignored and why, at least once every six months, it is important to declutter your cosmetics: remove products that have been open for too long, which could pose a risk to the skin. This is especially true for cosmetics used in delicate areas (eye contour, lips, face in general), which have a high percentage of water or sensitive active ingredients (such as vitamin C serums).

How it is determined, how it is indicated, and where it is located

The PAO is established by laboratories through specific stability and microbiological challenge tests, which simulate repeated opening of the product and exposure to real-use conditions. Only after these verifications can the company determine how many months the product can be safely used for.

To clearly communicate this information to the consumer, the PAO is indicated on the label using a mandatory graphic symbol: an open jar accompanied by a number followed by the letter M (which stands for months), for example: 6 M, 12 M, 24 M.

By law, the PAO symbol must always be clearly visible, legible, and indelible, easily identifiable by the consumer. It cannot be hidden or so small as to be unreadable.

On SKINIUS products, it is generally found on the back or bottom of the carton, near the barcode or the INCI. On very small packaging, it is usually shown in smaller characters, but still compliant with legibility standards.

What the law states

The indication of the PAO is regulated by Regulation (EC) 1223/2009 on cosmetic products. According to this regulation:

products with a minimum durability of more than 30 months do not need to show an expiry date, but must indicate the PAO;
products with a minimum durability of less than 30 months must indicate the minimum durability date (the actual expiry date) and may also indicate the PAO.

PAO, Shelf Life, Warranty Period and Batch Number: what's the difference?

PAO - Indicates for how many months a product remains safe and usable after opening the package
Shelf Life - Minimum guaranteed shelf life of an unopened cosmetic, indicating the period during which it maintains its characteristics unchanged
Warranty Period - This is not a cosmetic term, but a commercial guarantee of conformity provided for by the Consumer Code
Batch Number - Alphanumeric code that identifies the production cycle, ensuring the traceability and quality control of each product

Where the PAO is not required: single-dose or single-use products

There are categories of products for which PAO is not required, precisely because their format implies immediate use. This is the case for:

single-dose samples (designed for immediate testing, so-called "single use")
single-use ampoules for hair or face
sheet masks
pre-soaked eye patches and lip patches
individually wrapped cosmetic wipes

In all these cases, you will not find the PAO symbol because the product is designed to be used only once or entirely within a very short time, so long-term storage is not intended.

How to store cosmetics to preserve their shelf life

Even when respecting the PAO, proper storage makes a difference.
Here are some simple tips:

Always close products tightly after each use
Oxygen and humidity are among the main factors that can degrade a formula, so it is essential to carefully close jars, tubes, and bottles.
If the product comes with a protective tab or "disc" inside the jar, do not throw it away.
It will help protect the formula between uses, keeping the product more isolated from air and contamination.
Store cosmetics in a cool, dry place.
Keep them away from heat sources (e.g., radiators or hair dryers) and direct sunlight: light and heat accelerate the oxidation of ingredients.
Always wash your hands
It is always advisable to use cosmetics on clean surfaces and sanitized hands before application, or, if you prefer, you can use a clean spatula or applicator that should always be washed between uses.
Do not transfer cosmetics to non-original containers
Although it may seem practical, transferring a cream or serum to another container compromises the stability and safety of the formula. The original packaging is designed to protect the product: it is best not to alter it.
Do not share cosmetics with other people
While it may be a kind gesture between friends, sharing certain cosmetics, particularly mascara, eyeliner, gloss, and lip products, significantly increases the risk of bacterial contamination.
Do not store products in the car, bag, or backpack for long periods
Temperature and humidity in car interiors or bags can vary greatly throughout the day, especially in summer. This can quickly deteriorate creams, lip balms, and makeup.
For products with droppers, never rest the dispenser on your skin
This is a very common but risky habit: the dropper should be kept clean, never touching the face or hands directly, to avoid reintroducing bacteria into the bottle.
Keep powdered makeup products (eyeshadows, powders, blushes) always closed
Even powders can collect humidity and environmental dust if left open. Always closing the lids helps keep them dry and safe for longer.
For stick products (lipsticks, concealers, SPF), clean the surface regularly
Simply wipe gently with a clean tissue to remove any surface residue and keep the product more hygienic, especially if you apply it directly to your lips or skin.
Use products consistently
Don't keep them open for years just "because you feel bad finishing them." Your skin always deserves active, fresh formulas and safe performance.

A LITTLE HELP FOR YOU

Download labels to track the PAO of your cosmetics

To make it easier for you to monitor the PAO of your cosmetics, we have created a ready-to-print PDF sheet with 6 labels to attach to your cosmetics and mark the date by which to use them safely. You can:

print it on regular paper and attach it with a piece of tape to the product
print it on an adhesive sheet to apply directly to the packaging

Or use a permanent marker and write the opening date directly on the packaging. This way, you'll always have at hand the date by which to use your products safely.

A simple gesture that will help you take even more care of your beauty routine.

Download PDF sheet