periodafteropening

Period after opening, commonly abbreviated PAO, is a labeling convention used on cosmetic products to indicate how long the product remains usable and safe after it is first opened. The PAO represents a specific period, usually stated in months, during which the product is expected to maintain its quality under proper storage.

The PAO symbol is typically shown as an open, partially filled jar accompanied by a number and the letter M (for months), for example 12M. This tells consumers to use the product within that many months after first opening. If a product does not carry a PAO, it may instead display an expiry date, or the manufacturer may indicate that the product is stable for a defined period without opening.

Regulatory and labeling notes vary by region. In many jurisdictions the PAO is commonly used on cosmetics and is required for products lacking a separate expiry date. A PAO is not a guarantee of safety after the period ends; it reflects practical stability after opening and can be affected by storage conditions, contamination, and usage patterns. Products with sterile packaging or those that are microbiologically stable may not require a PAO.

Determining the PAO involves stability testing and expert assessment by the manufacturer. Consumers should monitor changes in scent, color, or texture and discard the product after the indicated PAO or sooner if problems arise. PAO differs from best-before or use-by dates, which relate to overall product safety or quality before opening rather than after.