PAO stands for Period After Opening. It's the little open-jar drawing with 6M, 12M or 24M inside. The M means months, so 12M tells you to finish the product within 12 months of the day you first open it.
Based on MFDS Cosmetics Act Article 10 · Updated October 2026
The confusing part is that labels often carry another date next to it. Add a manufacture date and an expiry date to the mix and it gets hard to tell which number decides when to toss the product. The three marks mean different things, and Korean law pairs them in a set way. Once you know the rule, they're easy to read.
Three markings: what sets them apart
Marking
Meaning
Required?
Expiry date
The last day the product can be used while still sealed
Required (either this or a PAO)
PAO (Period After Opening)
How many months the product lasts once opened
Required (may replace the expiry date)
Manufacture date
The date the product was made
Required alongside a PAO
Korea's Cosmetics Act requires either an expiry date or a period after opening (Article 10). If a brand picks the PAO, it also has to print the manufacture date. So most real labels show one of two things: a single date such as "use by 2027.05", or a PAO mark paired with a manufacture date.
The rules say an expiry date is written as a full date with words like "use by" or "until" next to it (Enforcement Rule, Annex 4). A date carrying those words is the expiry date. A bare date with no words around it is most likely the manufacture date.
Reading the PAO symbol
The most common way to show a PAO is a number and an M inside an open jar symbol. The rules also allow it in words, such as "period after opening: 12 months", so either form counts (Enforcement Rule, Annex 4).
6M12M24M36M
6M means six months after opening. You'll see it a lot on mascara and eyeliner.
12M is twelve months and shows up often on liquid foundation and lipstick.
24M is twenty-four months and is common on toners and creams.
36M is thirty-six months and appears on some powder products.
One thing to watch: the PAO clock starts the day you open the product. If it sat sealed in a drawer for a year, the count begins when you finally open it. If the label also shows an expiry date, though, that date still ends things even for a sealed product.
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Typical PAO by product category
Here are the PAO ranges you'll typically see for each product type. Products within the same type still vary, so your own label always comes first.
Category
Typical PAO
Signs it has gone off
Toner
12-24M
Cloudiness or sediment, a sour smell
Essence / Serum
12-18M
Color change (vitamin C browning in particular), separation
Cream / Lotion
12-24M
Layers separating, a sheen on the surface, a rancid smell
Sunscreen
12M (within the unopened expiry date)
Layers separating, possible drop in protection
Mascara / Eyeliner
3-6M
Clumping, a sour smell, stinging
Liquid foundation / BB cream
6-12M
Layers separating, color shift
Lipstick / Lip balm
12-24M
Crystals or an oily film on the surface, rancidity
Powder makeup
24-36M
A hardened surface, mold
Shampoo / Body wash
12-24M
Separation, a change in thickness, mold
Six signs a product has gone off
Even with time left on the label, stop using a product if you notice any of these. The date is only a guide, and poor storage can spoil a product sooner.
The color has changed. It looks darker or yellower than when you bought it. A vitamin C serum that turns brown or orange has started to oxidize.
It has separated or settled. If shaking doesn't bring it back together, the emulsion holding water and oil has broken.
It smells off. Sour, rancid or moldy smells that clearly differ from the original scent are a red flag.
It has thinned out or hardened. A texture that's noticeably different from day one is a sign.
There's oil on top. In creams, a greasy layer rises and floats on the surface.
It suddenly stings. A product you always got on with now brings stinging, redness or itching. Stop right away.
Storing cosmetics: tips to make them last
Keep them out of sun and heat: a drawer away from sunlight suits glass bottles. Bathrooms run warm and humid, which some products don't like.
Keep the opening clean: scoop jar creams with a spatula instead of your fingers and wipe pump nozzles now and then.
Oxidation-sensitive products like vitamin C: pick ones in dark containers and use them up fairly quickly once opened. It's more common than you'd think. Of the 2,426 full ingredient lists we've collected, 173 contain pure vitamin C (ascorbic acid).
Fridge only if the label says so: preservative-free or natural-concept products sometimes call for it. Ordinary cosmetics keep their emulsion better at room temperature, so follow the label.
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Labels on cosmetics bought overseas
Products bought abroad follow different labeling rules from Korea.
The EU and UK require an expiry date on products lasting under 30 months, and let products lasting 30 months or more show only a PAO (Cosmetics Regulation 1223/2009).
The US sets no expiry-labeling requirement for ordinary cosmetics. Only OTC products such as sunscreen and acne treatments need one.
Japan can waive the marking where stability is proven for three years or more.
Products bought from overseas often have less time left on the expiry date than ones sold through official Korean channels. Check the date before you buy.
Editorial Tip
Note the opening date
"The PAO starts the day you open a product, so jot the month inside the cap or on the label when you crack open something new. Remember 6M, 12M and 24M and you can read most labels."
— Beauty Dupe Editorial
Frequently asked questions
How do I read the expiry labels on cosmetics?
Look for the expiry date and the PAO. One of the two is always there. A date marked with words like "use by" is the last day the sealed product can be used. A number like 12M inside the open-jar drawing is the PAO, so use the product within 12 months of opening it.
My mascara is marked 6M. Can I keep using it past six months?
Mascara touches the eye area, so it deserves the strictest treatment. After six months the risk of bacterial growth climbs, and with it the chance of conjunctivitis or a stye. With mascara, stick to the PAO.
If only a manufacture date is printed, how long can I use the product?
Under the current Korean rules, products that use a PAO print the manufacture date alongside it. So if you see a manufacture date, look nearby for the open-jar drawing or the words "period after opening". Once opened, follow that PAO. For a product left sealed for a long time, check the signs of spoilage below first.
What happens if I use a product past its expiry date?
Usually it works less well, bacteria multiply and oxidized byproducts build up. Reactions range from mild irritation to allergy or contact dermatitis.
Do samples follow a PAO too?
Yes. A sample of the same formula carries the same PAO. Single-use sachets meant for one or two applications are best used right after opening.
Skin Warning
A product that has gone off can cause anything from mild irritation to allergy or contact dermatitis. If you notice separation, an off smell or sudden stinging, stop using it right away.
