How Does the PAO Symbol Work? The 2026 Guide to Cosmetics' Period After Opening
Shelf Life Guide•December 2024
What does that little open-jar symbol on the bottle mean, and how long can you actually use a product after opening? This article explains the PAO (Period After Opening) symbol in detail so you can manage your cosmetics' usage windows scientifically.
What is PAO?
PAO (Period After Opening) is the usage window after opening, a labeling standard mandated in the EU. The number inside the little open-jar symbol on the bottle (such as 6M or 12M) indicates how many months the product should be used up within after opening.
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Typical PAO windows for common cosmetics
| Product category | Period after opening | Notes |
|---|---|---|
| Mascara | 3-6 months | A liquid environment breeds bacteria easily; replace every 3 months |
| Liquid eyeliner/eyeliner pencil | 3-6 months | Touches the eyes, so hygiene requirements are high |
| Liquid foundation | 6-12 months | Water-based products spoil easily |
| Sunscreen | 6-12 months | UV filters oxidize and lose effectiveness easily |
| Serums | 6-12 months | Active ingredients degrade easily |
| Face cream/lotion | 6-12 months | Depends on ingredients; vitamin C products run shorter |
| Lipstick/lip gloss | 12-18 months | Oils are relatively stable |
| Pressed powder/loose powder | 12-24 months | Dry powders rarely breed bacteria |
| Eyeshadow palettes | 12-24 months | Lasts longer if kept away from moisture |
| Perfume | 24-36 months | Alcohol acts as a preservative, but the scent will change |
Important reminder
These windows are recommendations assuming proper storage. If a product develops an unusual smell, a color change, or a texture change, stop using it immediately even if it hasn't reached the limit.
Why does the shelf life shrink after opening?
Unopened, a cosmetic sits in a sealed, sterile environment and stays stable for years. Once opened, it faces the following challenges:
Bacterial contamination
Every use carries bacteria from your fingers and brushes into the product — especially water-based products like mascara and foundation, which breed bacteria more easily.
Oxidation
Once exposed to air, oils, vitamins, and other active ingredients oxidize, reducing effectiveness or even producing harmful compounds.
Evaporation
Water gradually evaporates after opening, making the texture drier, harder to spread, and less effective.
Light exposure
Light accelerates the breakdown of certain ingredients, especially photosensitive ones like vitamin C and vitamin A — which is why storing products away from light matters.
How to extend the shelf life of your cosmetics
Proper storage habits
- ✓ Store away from light: keep cosmetics in a cool place, out of direct sunlight
- ✓ Keep them dry: humid environments like the bathroom speed up degradation
- ✓ Seal them tightly: close the cap right after use to limit air exposure
- ✓ Use tools: scoop with a spatula or apply with brushes instead of fingers
- ✓ Label the date: mark the opening date on the bottle for easy tracking
Habits to avoid
- ✗ Keeping cosmetics in the bathroom (hot and humid)
- ✗ Digging into jar products with your fingers
- ✗ Sharing eye or lip products with others
- ✗ Leaving products in the car (high temperatures)
- ✗ Using products past their PAO window
Signs of spoilage: stop using the product immediately if you see these
Change in smell
A rancid, oily, or otherwise off smell means the oils have oxidized and gone bad.
Change in color
The product darkening, turning yellow, or separating into layers with sediment suggests the ingredients are breaking down or oxidizing.
Change in texture
Becoming too thin, clumpy, water-oil separated, or hard to spread means the product is no longer stable.
Skin reaction
If stinging, redness, itching, or an allergic reaction appears after use, stop immediately and wash it off.
How to manage your cosmetics' shelf life
Managing the shelf life of a large collection can be a chore. Here are a few practical tips:
Use the My Vanity feature
BeautyChecker's My Vanity feature helps you record all of your cosmetics and automatically calculates opening dates and sends expiry reminders.
Label the opening date
Put a sticker on the bottle with the opening date and the recommended usage window so you can check it at any time.
Declutter regularly
Go through your cosmetics once a quarter and discard anything expired or spoiled before you accidentally use it.