The Period After Opening is a key element of cosmetic safety information. It tells consumers how long they can safely use a cosmetic product after opening its primary packaging for the first time. Unlike a fixed expiry date, which applies whether the product is opened or not, the PAO countdown starts at the moment the product comes into contact with air and potential contaminants.

The PAO helps consumers understand how long the product maintains its safety, stability, and performance during real-life use.

Visual Representation and PAO Marking on Packaging

Cosmetic packaging displays the Period After Opening using the recognizable open jar symbol. This symbol resembles an opened container and appears on the label when a product requires PAO information.

Inside or next to the symbol, manufacturers indicate a number followed by the letter “M,” such as 6M, 12M, or 24M. The letter “M” stands for months. For example, a 12M symbol means the product remains safe and effective for 12 months after first opening.

In the European Union and many other markets, PAO marking is mandatory for cosmetic products with a minimum durability of more than 30 months.

The Scientific Basis of PAO and Cosmetic Stability

The PAO directly reflects the microbiological and physical stability of a cosmetic product after opening. Once the protective seal breaks, the product faces several risk factors that can affect safety and quality.

Microbial contamination occurs when microorganisms enter the product from air exposure, fingers, or applicators. Over time, this contamination can overwhelm the preservative system, reduce product quality, and increase the risk of consumer infection. The Period After Opening defines the period during which the product remains microbiologically safe under normal conditions of use.

Physical and chemical degradation also influence PAO determination. Exposure to oxygen and light can trigger oxidation of active ingredients, fragrances, and oils. These changes may alter the product’s color, odor, texture, and effectiveness. The PAO reflects the point at which such degradation may compromise product performance.

Difference Between PAO and Expiry Date

Consumers often confuse the PAO with the expiry date, but these two markings serve different purposes and apply to different product lifecycles.

A fixed expiry date, also known as the “Best Before End” date, applies to cosmetic products with a shelf life of 30 months or less. This date indicates when the product should no longer be used, regardless of whether it has been opened.

The Period After Opening applies to products with a shelf life longer than 30 months. Once the consumer opens the product, the PAO becomes the controlling safety reference. Even if the product is newly manufactured, the user must stop using it after the indicated Period After Opening period, such as 6 or 12 months after opening.

Why PAO Is Essential for Consumer Safety

The Period After Opening serves as a practical consumer safety guideline. It protects users from risks linked to microbial growth, ingredient degradation, and reduced preservative effectiveness after opening. By following the PAO, consumers help ensure that cosmetic products remain safe, stable, and effective throughout their intended period of use.

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