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0 of 20 productsWhat is PAO?
PAO is short for Period After Opening. Nearly every skincare product carries a small symbol shaped like an open jar with a number inside it, followed by the letter M. That number is how many months the product stays safe and effective after you first open it.
An open jar marked 12M means the product is good for twelve months after opening. If you opened it in January, it is best finished by the following January, even if the printed expiry date is further away.
This matters because the unopened expiry date and the PAO clock are two different things. A serum might be fine sealed in a drawer for two years, but once air and your fingers get in, the PAO period is what counts. When there is no PAO symbol printed, the reference below gives you a sensible guide for each type of product.
Common PAO periods by category
Use these as a rough guide when a product does not show its own open jar number. Preservative free and natural formulas usually sit at the shorter end.
| Product | Typical PAO | Good to know |
|---|---|---|
| Cleanser | 6 to 12 months | Water based and gentle, generally long lasting. |
| Toner | 6 to 12 months | Watch alcohol free and hydrating toners, which spoil sooner. |
| Serum | 6 to 12 months | Vitamin C serums oxidise fast, often 3 months once opened. |
| Moisturiser | 6 to 12 months | Jars go quicker than pumps because fingers add bacteria. |
| SPF | 12 months | Replace yearly. Heat and humidity break down filters faster. |
| Eye cream | 6 months | Used near the eyes, so freshness matters more here. |
| Sheet mask | By printed date | Single use. Follow the pouch date rather than a PAO. |
| Exfoliant (acids) | 6 to 12 months | Acids can weaken over time and become less effective. |
| Natural or preservative free | 3 months | Little or no preservative means a much shorter life. |
A note for hot and humid climates
If you live somewhere warm and sticky, your products age faster than the label assumes. Bathroom shelves are the worst spot, since every shower turns them into a sauna. Keep your actives and sunscreen somewhere cool and dark, and when in doubt, trust your senses. A change in smell, colour or texture means it is time to let go.
Keep going
Once you know what is still good, make the most of it.