Have you ever noticed a small symbol on your makeup or skincare products that looks like an open jar with a number followed by the letter “M”? For example, you might see “6M,” “12M,” or “24M” printed near the bottom of a bottle or compact. This simple icon carries important information about product safety and effectiveness. Known as the Period After Opening (PAO) symbol, it tells you how long a cosmetic product remains safe to use after it has been opened.
The open container symbol was introduced to help consumers better understand product shelf life. Unlike food products, cosmetics do not always display traditional expiration dates. Many beauty items are designed to remain stable for years while unopened. However, once exposed to air, light, bacteria, and repeated contact with fingers or applicators, their stability can change. The PAO symbol addresses this by focusing specifically on what happens after the seal is broken.
The number inside the open jar symbol represents the recommended number of months the product should be used after opening. For example, “12M” means the product is considered safe and effective for 12 months once opened. After that period, the formula may begin to degrade, preservatives may lose effectiveness, and the risk of contamination can increase.
Why does this matter? Using expired cosmetics can lead to reduced performance and potential skin irritation. Mascara is a great example. Most mascaras carry a “3M” or “6M” label because the moist, dark environment inside the tube can quickly become a breeding ground for bacteria. Continuing to use old mascara can increase the risk of eye infections. Similarly, expired liquid foundations or creams may separate, change texture, or develop an unusual odor — all signs they should be discarded.
Skincare products like moisturizers, serums, and sunscreens also rely on active ingredients that may lose potency over time. Sunscreen, in particular, must maintain its stability to provide adequate UV protection. If used beyond its recommended PAO period, it may not deliver the level of protection stated on the packaging.
The presence of the open jar symbol is especially common in regions where cosmetic regulations require manufacturers to provide shelf-life information when a product’s durability exceeds 30 months unopened. Instead of listing a fixed expiration date, brands provide the PAO symbol to guide consumers once the product is in use.
To make the most of your beauty products, it’s helpful to develop a simple habit: write the opening date on the packaging with a small sticker or marker. This allows you to track usage and avoid guessing months later. Proper storage also extends product life. Keep cosmetics away from excessive heat, humidity, and direct sunlight, as these conditions can accelerate degradation.
While it may be tempting to use a favorite product long past its prime, paying attention to the open container symbol protects both your skin and your investment. Cosmetics are carefully formulated for performance and safety within a specific timeframe. By understanding the meaning behind that small jar icon, you can maintain healthier skin, prevent irritation, and ensure your beauty routine remains both effective and safe.