Period After Opening (PAO)

The Period After Opening (PAO) is a labeling requirement under the EU Cosmetics Regulation (EC 1223/2009) that indicates how long a cosmetic product can be safely used after it has been first opened by the consumer. The PAO is represented by the "open jar" symbol (an icon of an open cosmetic pot) accompanied by a number and the letter "M" indicating months — for example, "12M" means the product should be used within 12 months of first opening.

The PAO is mandatory for products with a minimum durability of more than 30 months. Products with a minimum durability of less than 30 months must instead display a "best before" date preceded by the hourglass symbol or the words "best used before the end of." Products that do not deteriorate over time (e.g., solid soaps, single-use sachets) are exempt from both requirements.

Determining the appropriate PAO requires stability and microbiological testing, including challenge tests (preservative efficacy tests) conducted under accelerated aging conditions. Factors affecting PAO include the preservative system, product type (emulsion vs. anhydrous), packaging (airless pump vs. open jar), water activity, and pH.

Common PAO values in the industry range from 3M (for sensitive formulations or products used near the eyes) to 24M (for stable, well-preserved products). The PAO determination should be supported by stability data in the Product Information File (PIF) and reviewed as part of the Cosmetic Product Safety Report (CPSR).