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Skincare shelf life, PAO and preservatives: the rules and how to set them

What shelf life and the open jar symbol mean, which date your label needs in the EU and the US, how stability tests set the numbers, which preservatives are allowed at what level, and when "preservative-free" is a claim you can make.

Not legal adviceThis guide summarizes official texts as of October 2026. Your safety assessor, Responsible Person or importer has the final word on what goes on your label.

Short answer

Shelf life is how long an unopened product stays safe and works as intended; the PAO (period after opening, the open jar symbol with "12M" or similar) is how long it stays good once opened. In the EU and UK, a product that keeps 30 months or less must show a date of minimum durability ("best used before the end of" or the hourglass symbol), and a product that keeps more than 30 months shows the PAO instead. The US has no expiry date rule for most cosmetics, but products that are also drugs, such as sunscreens and acne treatments, need an expiration date backed by stability data. Shelf life comes from stability testing, and the preservative system, proven by a challenge test (ISO 11930), keeps a water-based product free of microbes; in the EU only preservatives in Annex V are allowed, at set maximum levels such as 1% for phenoxyethanol.

Shelf life, expiry, best-before, PAO

Shelf life (minimum durability): How long the product, unopened and stored as directed, keeps its quality and safety: no separation, no color or smell change, actives within specification, no microbial growth. Many skincare products are set at 24 to 36 months, but the number must come from the product's own stability data.
Date of minimum durability (best-before): The date printed on the pack until which an unopened product keeps its initial function. In the EU it can be written after "best used before the end of" or after the hourglass symbol.
Expiration date: The US drug term: the date after which a drug may no longer meet its standards. Required on US over-the-counter drugs, such as sunscreens.
PAO (period after opening): How long the product can be used safely after it is first opened, shown by the open jar symbol with a number of months, such as 6M or 12M. It depends on the formula, the preservative system and the packaging.
Batch number (lot code): The code that links a unit to its production record. Required on EU labels and needed everywhere to trace complaints and recalls.

Market by market rules for dates on the label are summarized in INCI lists, PAO and expiry on labels and label requirements by country. This guide goes deeper on where the numbers come from.

EU and UK: date or PAO

Article 19(1)(c) of the EU Cosmetics Regulation (Regulation (EC) No 1223/2009), which Great Britain kept in its own version, sets the rule:

Minimum durability	What the label must show	Example
30 months or less	The date of minimum durability: month and year, or day, month and year, after the hourglass symbol or "best used before the end of"	A vitamin C serum that keeps 18 months: "best before end 04/2028"
More than 30 months	No date needed. Instead the PAO symbol (open jar) with the period in months or years	A cream that keeps 36 months: open jar with "12M"

The PAO only applies where it makes sense. Industry guidance and safety assessors treat it as not relevant for single-use products and packs that cannot be opened in normal use, such as some aerosols. Your safety assessor decides.
You may show both. Many brands print a best-before date and a PAO even when the rule only asks for one, because retailers and customers like both.
Storage conditions. If the shelf life depends on how the product is stored ("store below 25 degrees C"), say so on the label.
The numbers belong in the safety file. The cosmetic product safety report (CPSR) must cover the stability of the product under reasonably foreseeable storage conditions, and the PAO or date must match that evidence.

US: cosmetics vs OTC drugs

The FDA says no US law or regulation requires cosmetics to have a specific shelf life or an expiration date on the label. The manufacturer is still responsible for making sure the product is safe for as long as it is likely to be used, and the FDA says a product that is not can be adulterated or misbranded. MoCRA adds a duty to keep adequate safety substantiation for every product, and stability data is part of it. See MoCRA compliance.

Drugs are different. A product that is both a cosmetic and an over-the-counter (OTC) drug, such as an SPF moisturizer, a sunscreen or an acne treatment with salicylic acid, must follow drug rules: stability testing and an expiration date (21 CFR 211.137). That rule includes a narrow exception, not enforced for OTC drugs without dosage limits that are shown to be stable for at least 3 years, but most sunscreen brands print an expiration date anyway. See sunscreen regulation and cosmetic vs drug claims.

Retailers and marketplaces can be stricter than the law. Many ask for a printed expiration or best-before date and a minimum remaining shelf life when stock arrives at their warehouse. Check the seller rules for each channel; for Amazon, see selling skincare on Amazon. If you sell in several markets with one pack, printing a best-before date and a PAO covers most cases.

How stability data sets shelf life

A stability test stores samples of the product in its final container under several conditions and checks them at set intervals. ISO publishes guidelines for it (ISO/TR 18811), and the details are in our stability and compatibility guide and stability testing article. The basic steps:

Fix the final formula and container
Stability is tested in the real pack, because the container changes the result: a clear bottle lets light in, a jar lets air in, some plastics absorb fragrance or lose water.
Store samples under several conditions
Typical sets are a cold condition (about 4 to 5 degrees C), room temperature (about 25 degrees C), a warm condition (about 40 to 45 degrees C), freeze and thaw cycles and light exposure. Hot conditions speed up changes so problems show sooner.
Check at intervals
Appearance, color, odor, pH, viscosity, separation, weight loss, active content where it matters (vitamin C, retinal), and microbiology. Results are compared with the product specification.
Read the result as a shelf life
If the product passes at all conditions over the test period, the stability data supports a shelf life. Accelerated (hot) results are often used to estimate shelf life before real-time data is complete. A common industry rule of thumb treats 3 months at 40 to 45 degrees C as a sign of roughly 2 years at room temperature; it is a rule of thumb, not a regulation, and real-time data should confirm it.
Set the PAO
The PAO comes from the in-use risk: how much air, water and fingers reach the product after opening, how strong the preservative system is (the challenge test) and how fast actives degrade once opened. Jars usually get shorter PAOs than airless pumps; 6M or 12M are common for face care.
Write it into the file
The shelf life, PAO, storage conditions and test report go into the safety report (CPSR in the EU and UK) and the brand's safety substantiation file (US).

ExampleA 30 mL vitamin C serum (15% ascorbic acid) in a clear glass dropper turns yellow-brown after 6 weeks at 40 degrees C, and its vitamin C content falls below specification. The same formula in an amber airless pump passes 12 weeks. The brand chooses the airless pack, sets a 24-month shelf life from the data, prints "best before end" because 24 months is under 30, and adds a 6M PAO because vitamin C keeps degrading once opened.

Preservatives and their limits

A water-based product (toners, serums, gels, lotions, creams) can grow bacteria, yeast and mold after opening, and even in the factory if hygiene slips. A preservative system keeps the count down for the whole shelf life and PAO.

EU and UK: a positive list. Only substances listed in Annex V of the Cosmetics Regulation may be used as preservatives, at or below the listed maximum, with any listed conditions and warnings. Selected entries:

Preservative	EU maximum in the finished product	Conditions
Phenoxyethanol	1.0%	None listed
Methylparaben, ethylparaben	0.4% for one ester, 0.8% for mixtures (as acid)	None listed
Propylparaben, butylparaben	0.14% combined (as acid)	Not in leave-on products for the diaper area of children under 3 (the regulation says "nappy area"), with a warning on leave-on products for children under 3
Isopropyl-, isobutyl-, phenyl-, benzyl- and pentylparaben	Not allowed	Prohibited since 2014 (Regulation (EU) No 358/2014)
Benzoic acid and sodium benzoate	2.5% rinse-off, 1.7% oral care, 0.5% leave-on (as acid)	Works best at acidic pH
Sorbic acid and potassium sorbate	0.6% (as acid)	Works best at acidic pH
Dehydroacetic acid and sodium dehydroacetate	0.6% (as acid)	Not in sprays
Benzyl alcohol	1.0%	Also a fragrance allergen when used for scent
Salicylic acid (as a preservative)	0.5% (as acid)	Not for children under 3, except shampoos; not in sprays that can be inhaled
Methylisothiazolinone	0.0015%	Rinse-off products only
Formaldehyde releasers (for example DMDM hydantoin)	Entry-specific limits	Label "releases formaldehyde" if total released formaldehyde is above 0.001% (since 31 July 2024 for new products; all products since 31 July 2026, Regulation (EU) 2022/1181)

Always check the current consolidated Annex V before you finalize a formula, because entries change through regular amendments (see EU cosmetics regulation).

US: no positive list. The FDA does not approve cosmetic preservatives and restricts only a few substances in cosmetics, so the brand must make sure each product is safe. Several states have their own bans: California and Washington ban formaldehyde in cosmetics, and Washington bans intentionally added formaldehyde releasers such as DMDM hydantoin from January 1, 2027. See Prop 65 and state ingredient bans. A formula built to the EU list is usually the simplest way to sell in both markets; see reformulating for the US and EU.

Choosing a preservative system

Start from the product type
Water-based products need a full system. Anhydrous products (face oils, balms) have little microbial risk but need antioxidants against rancidity. Products with very high alcohol or very low water activity may need less.
Match the pH
Organic acids (benzoic, sorbic) only work in acidic products; phenoxyethanol works over a wider pH range. Your chemist picks the system for the formula's pH.
Check every target market
Use preservatives allowed in all your markets at the strictest limit. A brand selling in the EU, US, Korea and Japan usually builds to the EU list and checks the others.
Think about the claims you want
If you plan "paraben-free" in the US, avoid parabens; if you plan "no formaldehyde releasers", avoid them. In the EU, avoid "free from parabens" claims anyway (see below).
Use boosters if needed
Multifunctional ingredients such as ethylhexylglycerin, caprylyl glycol or 1,2-hexanediol are not on Annex V but help the preservative work at a lower dose. They count as protective ingredients for "preservative-free" claims in the EU.
Prove it with a challenge test
ISO 11930 adds bacteria, yeast and mold to the product and measures how fast the system reduces them over 28 days. EU and UK safety assessors usually want it, and it is essential for jars, natural formulas and anything sold as preservative-free. See challenge test, microbiology and heavy metals.

Preservative-free and self-preserving claims

Customers like "preservative-free". Regulators like evidence. The European Commission's technical document on cosmetic claims (the working group guidance used to apply Regulation (EU) No 655/2013) sets the EU line:

"Free from preservatives" should not be used when the product contains an ingredient that protects it against microorganisms, even one not listed in Annex V, such as alcohol, unless the responsible person has evidence, for example a challenge test of the formula without that ingredient, that it does not contribute to the protection.
"Free from parabens", "free from phenoxyethanol" should not be accepted, because they denigrate ingredients that are legal and safe when used within the rules.
"Free from" an ingredient that is banned (for example "free from corticosteroids") or that is typically not used in that product type is not allowed.

"Self-preserving" usually means the product has no Annex V preservative and relies on multifunctional ingredients, low water activity or packaging. That can be valid, but under the EU guidance it is still not "preservative-free" if those ingredients protect the product. A safer wording is the specific fact: "formulated without parabens" (US only), "in airless packaging to reduce contamination", or no claim at all.

For truly preservative-free products, the real tools are formula and pack: anhydrous formulas, single-dose packs, or a low-risk product assessed under ISO 29621 (a standard for identifying products with low microbiological risk). In the US, the FTC rule is the same in principle: a preservative-free claim must be true and must not mislead.

Airless and single-dose packaging

Packaging is part of the preservation plan:

Pack	What it does	Effect on PAO and preservatives
Open jar	Fingers and air reach the product every day	Needs a strong system and a challenge test; shorter PAO
Pump bottle or tube	Less contact; some air flows back	Moderate
Airless pump or airless jar	A piston or bag stops air coming back; no fingers in the product	Protects oxidizing actives (vitamin C, retinal); can support a longer PAO, but still needs a tested preservative system for a water-based formula
Single-dose sachet, capsule or vial	Opened once and used up	PAO not relevant; the closest thing to preservative-free for water-based products, at a higher cost per use

More in airless vs dropper packaging and minis and sachets.

Common mistakes

Copying a "36 months, 12M" from another product instead of using your own stability data.
Printing only a PAO on an EU product that keeps less than 30 months; it needs a best-before date.
Testing stability in a different container from the one you sell in.
Printing "preservative-free" on an EU product that relies on 1,2-hexanediol or alcohol to protect it.
Putting "paraben-free" and "phenoxyethanol-free" on EU packs, where the guidance treats them as denigrating.
Using a preservative allowed in the US but not on the EU Annex V list, then needing a reformulation to enter the EU.
Skipping the challenge test for a jar cream or a natural formula.
Forgetting that a sunscreen or acne product sold in the US needs a drug expiration date.

Checklist

I have stability data for this formula in its final container.
I know the shelf life from that data, and whether it is above or below 30 months.
EU and UK labels show a best-before date (30 months or less) or a PAO (more than 30 months).
The PAO matches the pack type and the challenge test result.
US drug products (sunscreen, acne) carry an expiration date.
Every preservative is allowed in every target market at the level used.
Warnings tied to preservatives are on the label (for example "releases formaldehyde" in the EU, if relevant).
The challenge test (ISO 11930) passed.
My "free from" claims follow the EU guidance and are true in every market.
Batch number and date are printed on every unit, and I know my marketplace's minimum remaining shelf life rule.

How KoreanOEM helps

KoreanOEM is a Korean skincare OEM and private label manufacturer: our formulation chemists in Busan develop the formula, and production runs in Korea under ISO 22716 (cosmetics GMP) with our own staff on site.

Stability data included for every ready library formula, so a brand using one of our 160+ library formulas does not pay for a new stability run. New stability runs for custom formulas are quoted per product.
Challenge test (ISO 11930) from USD 1,000 per formula through our lab and accredited partner labs; COA and microbiology for every batch; a separate accredited-lab microbiology report about USD 300 per product per batch if your importer asks for one.
Preservative systems built for your markets: tell us where you sell and which claims you want, and the chemists choose a system allowed in all of them.
Packaging that protects: stock bottles, jars, tubes, pumps and droppers in the unit price; airless and other custom containers sourced to your reference with a fit and leak check (USD 199 for up to 2 products); single-dose sachets from 3,000 units.
Batch number and date printed on every unit, and a label proof check before printing so the date or PAO format matches your market.

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Frequently asked questions

What is the difference between shelf life and PAO?

Shelf life is how long an unopened product keeps its quality, while the PAO (period after opening, the open jar symbol such as 12M) is how long it stays good once opened. Both should come from the product's own stability data and, for the PAO, the challenge test and pack type.

When does an EU cosmetic need a best-before date instead of a PAO?

Under Article 19 of Regulation (EC) No 1223/2009, a product whose minimum durability is 30 months or less must show a date of minimum durability. A product that keeps more than 30 months does not need a date and shows the PAO symbol instead.

Do cosmetics need an expiration date in the US?

No US law requires an expiration date on most cosmetics, although the manufacturer must make sure the product stays safe. Products that are also OTC drugs, such as sunscreens and acne treatments, must carry an expiration date based on stability testing.

How long does skincare last unopened?

Many skincare products are set at 24 to 36 months unopened, but the real figure comes from stability testing of that formula in its final container. Products with sensitive actives such as vitamin C can have shorter shelf lives.

What is the maximum phenoxyethanol allowed in the EU?

1.0% in the finished product, under Annex V of the EU Cosmetics Regulation. It is one of the most used preservatives in skincare and is often combined with a booster such as ethylhexylglycerin.

Are parabens allowed in the EU?

Some are: methylparaben and ethylparaben up to 0.4% each (0.8% in mixtures), and propylparaben and butylparaben up to 0.14% combined, with a restriction for the diaper area of children under 3. Isopropyl-, isobutyl-, phenyl-, benzyl- and pentylparaben have been banned since 2014.

Can I label my product preservative-free?

In the EU, only if no ingredient protects the product against microbes, including multifunctional ones like alcohol or 1,2-hexanediol, unless a challenge test shows they do not contribute. Anhydrous formulas and single-dose packs are the usual way to make a true preservative-free product.

Do natural or organic products need preservatives?

Yes, if they contain water. Plant extracts and ferments can feed microbes, so a natural water-based product needs a preservative system proven by a challenge test; organic standards allow only certain preservatives, which your chemist can choose.

Sources

Checked against these sources in October 2026. Rules and fees change; check with the authority or your importer before you sell.