The open-jar symbol (개봉 후 사용기한): how to read PAO on Korean packaging 개봉 후 사용기한

Period-after-opening, shown as an open jar with a number and M (for example 12M), is the maker's guide to how long the product is meant to be used after you first open it. On Korean packaging you may also see 개봉 후 and a month count. It is not a substitute for your nose and eyes: separation, colour shift or a new smell are reasons to stop earlier. Unopened expiry is a different date.

What 12M is counting

The clock starts when you break the seal, not when you bought it, and not when you first thought about using it. A cushion you pressed once in the shop tester is not your jar; your refill starts when you open yours.

Why sunscreen and vitamin C feel shorter

UV filters and unstable antioxidants can lose performance before the jar looks empty. The PAO is still a general window, not a lab assay of your bathroom cabinet. Heat and sunlight shorten the useful life further.

Korean wording

개봉 후 사용기한 is the phrase to look for — period of use after opening. Manufacture dates and 'use by' unopened dates may appear as 제조 or 유통기한. They answer different questions. The hub PAO tracker is a calculator from the day you opened a typical product type; the jar on your bottle wins if they disagree.

Cushions and pumps

Airless pumps help. Open jars and cushions with wet puffs are harsher environments. When in doubt, the smell test plus the printed M is the pair to use — not a viral 'it lasts three years' claim.

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✍️ Written & reviewed by the KoreaPlus Editorial team — dermatologist-informed, cosmetic-science researched & source-cited. Last reviewed: 2026-08-28.

General educational information using cosmetic structure-function wording — not medical advice. Always patch-test new actives. © KoreaPlus.