What Does the Period After Opening & Shelf Life Mean?
The period after opening (PAO) is the number of months a cosmetic remains safe and works as intended after you open it. Shelf life is how long it lasts sealed. The small open-jar symbol with “12M” inside means you have 12 months from the day you first open the product. The day you bought it doesn’t count.
Whether that symbol is printed on your jar depends on where the product is intended for sale. EU law requires a PAO or a hard date on almost every cosmetic. US law requires neither, except on products regulated as drugs, like sunscreen. If you shop in the US, most of the tracking falls on you.
TL;DR
| What you need from this page |
|---|
| PAO starts the day you open the product: “12M” means use it within 12 months of first opening. A sealed jar in your cabinet isn’t counting down yet. |
| Shelf life covers the sealed product; PAO covers the open one. A moisturizer can have a 36-month shelf life and a 12-month PAO. Whichever runs out first decides. |
| The US doesn’t require a PAO or an expiration date on cosmetics. Only over-the-counter drugs, like sunscreen and acne treatments, need an expiration date, and even they can skip it if stability data shows the product holds for at least three years. |
| The EU requires either a PAO or Best Used Before. A product that lasts 30 months or less gets a “best used before” date. Anything longer gets the open-jar PAO symbol. |
| Decide to throw away your cosmetics or products if you notice changes in smell & texture, regardless of the PAO. A change in smell, color, or texture means the product is done, whatever the date says. Write the opening date on the container so you’re not guessing later. |
Table of contents
- What the period after opening symbol means
- Period After Opening vs Shelf life vs Expiration date
- Is the PAO symbol Regulated by the FDA?
- How To Tell How Long A Product Lasts After Opening
- How Do Skincare Products Stay Fresh Without Decay?
- How brands work out a shelf life and PAO
- What Makes a product Decay Faster
- Habits That Keep Your Cosmetics Safe for Longer
What the period after opening symbol means
The PAO symbol is an open jar with a number and the letter “M” for months: 6M, 12M, 24M. It tells you how long the product stays safe and effective after you first open it.
You’ll usually find it on the back or bottom of the pack, near the ingredient list. The jar drawing is the same in every country, so it works without translation. The “M” stands for month.
So if your body butter says “12M” and you open it in January, plan to finish it by the following January.
Why start the clock at opening and not at purchase? Because opening changes everything for the product inside. Air gets in. So does moisture from a damp bathroom, plus whatever is on your fingers or your brush. A sealed jar can sit on a warehouse shelf for two years and come out fine. The same jar, opened and dipped into twice a day, ages on a much shorter timeline.
Period After Opening vs Shelf life vs Expiration date
Shelf life is how long a product lasts before opening.
Period after opening is how long it lasts once opened.
An expiration date is a fixed calendar date that applies whether the product is opened or not. In the EU, the label shows either a durability date or a PAO, depending on shelf life.
People use these three terms as if they mean the same thing. They don’t, and mixing them up is how a two-year-old open jar of face cream stays in a cabinet.
| Term | What it measures | When the clock starts | How it looks on a label | Required in the US? | Required in the EU? |
|---|---|---|---|---|---|
| Shelf life | Time the product stays safe sealed | Manufacture | Usually not printed | No | Shown as a durability date if 30 months or less |
| Period after opening (PAO) | Time the product stays safe once opened | First opening | Open-jar symbol with “6M,” “12M,” “24M” | No | Yes, if shelf life is over 30 months |
| Expiration date | A fixed last-use date | Set by the manufacturer | “EXP 03/2028” | Only for OTC drugs, unless stable 3+ years | As a “best used before” date if shelf life is 30 months or less |
A worked example: a moisturizer with a 36-month shelf life and a 12-month PAO. Sealed, it’s good for three years. Open it in month 30 and you don’t get another 12 months. You get six, because the shelf life ends first.
Is the PAO symbol Regulated by the FDA?
No. US law doesn’t require cosmetics to carry a PAO symbol, an expiration date or a stated shelf life. Brands are still legally responsible for making sure their products are safe for as long as people use them.
The FDA’s guidance on shelf life and expiration dating is direct about this: no US law or regulation requires a PAO symbol, an expiration date or a specific shelf life on a cosmetic label.
What the FDA does require is broader. Under the Federal Food, Drug, and Cosmetic Act, a brand must make sure its products are safe and not misbranded or adulterated. The FDA treats working out a product’s shelf life as part of that job, and has said that failing to do so may make a product adulterated or misbranded. Brands don’t have to share that shelf life data with the FDA, though.
The 2022 cosmetics law, the Modernization of Cosmetics Regulation Act (MoCRA), didn’t change any of this. It added facility registration, product listing and adverse event reporting, but no date or PAO labeling.
The exception: products regulated as drugs
Sunscreens, acne treatments and moisturizers with an SPF claim are regulated as over-the-counter (OTC) drugs, sometimes on top of being cosmetics. Drugs fall under 21 CFR 211, which requires stability testing and a printed expiration date.
There’s a carve-out most articles miss. OTC drugs with no dosage limit that stay stable for at least three years are exempt from the expiration date, as long as data backs it up (FDA Compliance Policy Guide Sec. 480.300). That’s why some sunscreens carry no date. If yours doesn’t, write the purchase date on the bottle and replace it within three years, sooner if it’s been in a hot car.
| US | EU | |
|---|---|---|
| PAO symbol required? | No, voluntary | Yes, if shelf life is over 30 months |
| Date required? | Only on OTC drugs like sunscreen, unless stable 3+ years | Yes, if shelf life is 30 months or less |
| Shelf life data shared with the regulator? | No | Held in the product file, available to authorities |
| Who enforces it | FDA | Each EU country’s national authorities |
How To Tell How Long A Product Lasts After Opening
Check for the open-jar symbol, then for a printed date. If neither is there, use the rough guide below, write the opening date on the container, and let smell, color and texture make the final call.
For products sold in the US, where the symbol is voluntary:
- Look for the open-jar symbol anyway: International brands often print it on US packs.
- Look for a printed expiration or “best before” date: On cosmetics, these are voluntary and not regulated by the FDA, so treat them as guidance.
- Use a rough guide when the label says nothing: See the table below.
- Write the opening date on the container: A marker or a strip of tape is enough. Without it, “I opened this in spring” turns into “I opened this at some point” fast.
- Check before each use: A change in smell, color, or texture overrides every symbol and date.
| Product | Rough guide after opening | Where the number comes from |
|---|---|---|
| Mascara | 3 months | Industry experts cited by the FDA |
| Liquid eyeliner | 3 to 6 months | Common industry guide |
| Creams and lotions | 6 to 12 months | Common industry guide |
| Liquid foundation | About 12 months | Common industry guide |
| Lipstick | 12 to 18 months | Common industry guide |
| Powder blush and eyeshadow | About 2 years | Common industry guide |
| Sunscreen with no date | Within 3 years of purchase | FDA CPG Sec. 480.300 |
These are working numbers, not legal ones. A product’s own PAO, when printed, beats this table.
How Do Skincare Products Stay Fresh Without Decay?
Before launch, manufacturers test how products age. This includes accelerated stability studies: samples are stored at elevated temperatures (40–45°C) and high humidity, simulating months or years of aging in weeks.
They also run freeze-thaw cycles (simulating winter-summer swings) and light exposure tests for photostability. At set intervals, products are checked for changes in color, odor, texture, pH, and ingredient potency.
Crucially, microbial challenge tests (preservative efficacy tests) are performed: the product is deliberately inoculated with bacteria, yeast, and mold to confirm the preservative system kills them off over time. Packaging compatibility is also checked to ensure containers don’t leach chemicals or let air and water in. All of this data informs the official shelf life.
Companies also build buffer time into distribution. If a lotion is stable for 36 months unopened, a brand might allow it only 24 months on the shelf, accounting for warehousing and retail delays. To move older stock first, many use a “first expiry, first out” rotation — products nearing their cutoff get discounted or withdrawn.
How brands work out a shelf life and PAO
Before launch, manufacturers age their products on purpose. In accelerated stability studies, samples sit at 40 to 45°C and high humidity, which packs months or years of aging into weeks.
Freeze-thaw cycles mimic a box shipped in winter and stored in summer. Light tests check whether sunlight breaks the formula down. At set intervals, someone checks color, odor, texture, pH, and how much of the active ingredients is left.
Then comes the test that decides most PAOs: the preservative challenge test. The lab deliberately adds bacteria, yeast and mold to the product and checks whether the preservative system kills them over the following weeks. That’s a direct simulation of what happens when you open the jar. Packaging gets tested too, to make sure the container doesn’t leach into the product or let air and water in.
Brands also build in a buffer for the supply chain. If a lotion is stable for 36 months sealed, a brand might allow only 24 months on the shelf, to cover warehousing and slow-selling stores. Many rotate stock “first expiry, first out,” so older units sell or get pulled first.
What Makes a product Decay Faster
Water, preservatives, packaging, storage and opening. Water-based products with light or no preservatives, in open jars, kept in warm bathrooms, go off fastest.
Ingredients. Water is what microbes need, so water-based formulas carry the most risk. The FDA notes that some “all natural” products may have an unusually short shelf life, because plant-derived ingredients can feed microbial growth, especially with non-traditional preservatives or none at all.
That’s an uncomfortable fact for a plant-based brand to print, and it’s still true. Preservatives are what buy a water-based product its PAO. A few of them are also common allergy triggers, which we cover in “what does hypoallergenic mean“. The answer isn’t “preservatives bad” or “preservatives good.” It’s matching the format to the formula.
Packaging: Pumps and tubes let less air and fewer fingers in than an open jar. Opaque containers block light.
Storage: Heat, humidity, and sunlight wear down both the formula and its preservatives. A cool, dry drawer helps. A sunny windowsill or a car in July does the opposite.
Opening: The biggest variable of all, and the reason the PAO exists.
Which cosmetics expire fastest
The pattern is consistent: wet products near your eyes go first, dry products last longest.
Mascara and liquid eyeliner lead the list. The wand goes from your lashes back into a dark, damp tube dozens of times a month. The FDA flags eye-area cosmetics as having a more limited shelf life than other products, and mentions industry advice to replace mascara three months after purchase.
Skincare with active ingredients like vitamin C or retinol loses strength once air gets in. You can sometimes watch it happen: a vitamin C serum that turns from clear to amber has oxidized.
Powders sit at the other end. With almost no water, there’s little for bacteria to grow in.
Do shampoo bars and other solid products expire?
Yes, but they age differently. Solid bars contain little water, so microbes have a harder time growing in them than in a liquid shampoo. A bar’s usual problems are going soft in a wet soap dish and, over a long time, oils going stale.
Water content is the reason. Cosmetic microbiologists measure “water activity,” the water that’s free for microbes to use. Under ISO 29621, the international standard for identifying microbiologically low-risk cosmetics, a water activity of 0.75 or lower is one of the markers of a low-risk product. Liquid shampoo is mostly water. A solid bar isn’t.
That doesn’t make a bar immortal. In practice, two things shorten its life:
- A wet dish: A bar left sitting in water turns soft and mushy and wears down fast. Store it on a draining dish, out of the shower stream, so it dries between uses.
- Time and air: Plant oils and butters can slowly go stale. If an old bar smells sharp or crayon-like instead of how it smelled new, it’s past its best.
Our shampoo bars and conditioner bars are solid, wrapped in compostable paper, and every ingredient is listed in our Tangie Ingredients Library. Check that list against anything your skin reacts to before you buy.
Expired products are waste twice
From a zero waste point of view, the PAO matters for one more reason. A half-used bottle that passes its PAO gets thrown out with the product still inside. That’s the formula wasted and the packaging wasted in one trip to the bin.
The fix is boring, and it works: buy sizes you’ll finish inside the PAO. A huge tub of body cream is only a good deal if you’ll use it within its 6M or 12M. Solid formats help here too. A bar you use every day is usually gone long before its oils have time to go stale, and there’s no bottle left over at the end. Our hair and body bars ship in paper, not plastic.
When something does go off, empty it, rinse the container, and recycle it if your local program takes that material.
Can you use a product after its period after opening?
Briefly and with care. Past the PAO, a product slowly loses strength and its contamination risk rises, but it doesn’t turn dangerous overnight. Never stretch eye products or anything with SPF.
The FDA calls expiration dates “rules of thumb”. A product stored badly, in heat or sunlight, can go off well before its date. One stored well may hold up a little past it.
Two exceptions. Eye products carry real infection risk, so don’t push them. And with sunscreen or any SPF claim, lost strength means lost protection, which you won’t see or smell.
Habits That Keep Your Cosmetics Safe for Longer
Most of these come straight from FDA consumer guidance:
- Throw out products that have changed. Check consistency, color, and smell. If mascara dries out, toss it. Never add water or saliva to revive it, since that puts bacteria straight into something you use near your eyes.
- Act fast on an eye infection. Stop using all eye-area products, throw out the ones you were using when the infection started, and see a doctor.
- Don’t share makeup, especially eye products. Store testers are more likely to be contaminated than products at home. If you must try one, use a fresh applicator like a new cotton swab.
- Keep applicators clean. Wash brushes with soap and water and replace sponges. Clean fingers matter too, for anything in a jar.
- Store products cool and dry, out of direct sun and never in a hot car.
- Buy from sellers you trust. Products from flea markets or unknown online sellers may be old, used, diluted or tampered with.
If you react to a new product even though it’s well within its date, the cause is more likely an ingredient than age. Our guide to how cleaning products and skin allergies are linked walks through the usual suspects and how to patch test.
Quick answers
What does 12M mean on a cosmetic? It’s the period after opening. Use the product within 12 months of first opening it.
Does the PAO start when I buy the product? No. It starts when you first open it. Until then, the product’s shelf life applies.
Do unopened cosmetics expire? Yes, though more slowly. Shelf life covers the sealed product. In the EU, products lasting 30 months or less must show a “best used before” date.
Is the PAO symbol required in the US? No. It’s voluntary on cosmetics. Only OTC drugs like sunscreen need an expiration date, and even they can skip it if stable for at least three years.
What does the hourglass symbol mean? It’s the EU date of minimum durability. The date next to it is the “best used before” date for products with a shelf life of 30 months or less.
Do shampoo bars expire? They last longer than liquid shampoo because they hold little water, but they can go soft if stored wet and their oils can go stale over time. Keep them dry between uses.
