Does Skincare Expire? The PAO Symbol, Shelf Life, and Warning Signs
Skincare runs on two clocks: shelf life while sealed and a period after opening. What the PAO symbol means, which products must carry a date, and the signs one has turned.
Yes, skincare expires, and it runs on two clocks: one while the product is sealed, and one that starts the day you open it. The small open jar symbol shows the second clock. In the US, cosmetics need no expiration date at all, but sunscreen and other over-the-counter drugs do. Below: does skincare expire under the rules, what the PAO symbol means, why vitamin C and retinol lose strength, how contamination starts, and how packaging changes the clock.
Does skincare expire? What the label has to tell you
In the US, the label may tell you nothing. The FDA states there are no U.S. laws or regulations that require cosmetics to have specific shelf lives or expiration dates on their labels. The agency treats shelf life as part of the manufacturer's responsibility for safety.
Drugs are different. Sunscreens and acne treatments are drugs under US law, and makeup or moisturizers with SPF labeling are both cosmetics and drugs. Drugs must be tested for stability and carry expiration dates, according to the same FDA page.
The EU takes a two-track approach. A product that stays good for 30 months or less must print a date of minimum durability. The date follows an hourglass symbol or the words "best used before the end of." A product that lasts longer than 30 months skips that date. Instead, it carries a period after opening, or PAO.
| Product | What the label must show |
|---|---|
| US cosmetic, such as a serum, cream, or cleanser | No date required |
| US drug, including sunscreen and acne treatments | An expiration date, unless stability testing supports at least three years |
| EU cosmetic that lasts 30 months or less | A date of minimum durability |
| EU cosmetic that lasts more than 30 months | A period after opening (PAO) |
What does the PAO symbol mean?
The PAO symbol is a small open jar with a number beside it, such as 6M or 12M. The M stands for months. The EU defines this as the period of time after opening for which the product is safe and can be used without any harm to the consumer. The period can be given in months, years, or both.
Three details matter. The clock starts when you open the product, not when you buy it. The number is the brand's own statement about the opened product. And it is not required where durability after opening is not a relevant concept.
Few people track the day they opened something, so write it on the carton. That one habit makes the symbol usable. The authors of a 2020 study of used cosmetics made a related point. Manufacturers should display expiry dates prominently, they wrote, and consumers should be able to identify the symbols used on product packaging.
A US product that prints a PAO symbol chose to. No US rule requires it. Read it as a disclosure from the brand.
Why actives break down: air, light, and heat
Every formula changes over time. The FDA lists the usual causes. Preservatives break down, emulsions separate, products dry out, and temperature changes and exposure to sunlight and air can change color and texture and cause a smell.
Some actives are more fragile than others. Vitamin C is the usual example. A 2024 paper calls stability the main drawback that limits vitamin C in cosmetic products. An older study measured why. Held at 45°C in air, ascorbic acid degraded faster as pH increased. The authors tied the pattern of loss to the dissolved oxygen in the sample, and emulsions slowed it down. Oxygen feeds the loss, and a higher pH speeds it up.
Retinoids have the best real-world data. A 2021 study measured 16 retinoid derivatives in 12 commercial cosmetics. After six months, retinoid content had declined 0 to 80 percent at 25°C and 40 to 100 percent at 40°C. Light caused more degradation than heat. Some products held less retinoid than their labels declared.
Notice what those numbers mean. For fragile actives, age often shows up as a smaller dose than the label promises. An old retinol serum may simply hold less retinol. Our retinol guide for beginners covers how to choose and use one.
Contamination: why an opened product is the weak point
Microbes get into products in two ways. A 2018 review of cosmetic preservation separates primary contamination, during manufacture, from secondary contamination, during consumer use. A preservative system has to protect the product in its closed pack and again throughout its use once it is open. The standard check is a challenge test, which adds known amounts of bacteria, yeasts, and molds to the product.
The FDA lists the routes in. They include contaminated raw materials, poor manufacturing, ineffective preservation, and packaging that does not protect the product. Poor shipping or storage counts too, and so does consumer use, such as dipping fingers into the product. Injuries from contaminated cosmetics are not common, the agency says, but they can be serious. Microbial contamination is a common reason for cosmetic recalls.
How much does use add? One UK study cultured donated, used lipsticks, lip glosses, eyeliners, mascaras, and makeup sponges. About 79 to 90 percent of the used products were contaminated with bacteria. The sponges averaged more than a million colony-forming units per milliliter. That study covered makeup, not serums. Treat it as a picture of how use adds microbes, not as a number for your moisturizer.
Eye products get the shortest life. The FDA says manufacturers usually recommend discarding mascara two to four months after purchase, because each use exposes it to bacteria and fungi. Never add water or saliva to a product that is drying out. That adds microbes and waters down the preservatives meant to control them.
How packaging changes the clock
Packaging decides how much air, light, and hand contact a formula meets after opening. The 2018 preservation review notes that jars and bottles are more likely to cause microbial contamination, while closed systems with airless pumps are less accessible. It adds that packaging can change how well a preservative works, through migration or adsorption.
Light is the other variable. In the retinoid study above, light did more damage than heat. That is the practical case for opaque packaging and for keeping the carton.
| Format | What meets the product after opening | What that means for you |
|---|---|---|
| Open jar | Fingers, air, and light at every use | The most exposure of any format |
| Airless pump | Little air, and no fingers in the reservoir | Less contact with the product that is left |
| Dropper bottle | Air at every opening, and a tip that may touch skin before it goes back in | Depends on how you handle the dropper |
| Sealed vial | Nothing until it is opened | Protection ends at the first opening |
A seal only protects a product until you break it. Our ampoules ship in crimp-sealed glass vials of 50 mL. Once you open one, it is an opened product like any other, and the same rules apply. The trade-offs between formats are covered in glass vial vs pump bottle, and the format itself in what an ampoule is.
Signs a product has turned
- The color, smell, or texture has changed since you opened it.
- An emulsion has separated into layers.
- A drug, such as a sunscreen, is past its expiration date.
- A sunscreen has no date and you bought it more than three years ago.
- A mascara is more than two to four months old.
- You used an eye product while you had an eye infection. The FDA says to throw those away.
For sunscreen, the FDA is blunt. Its guidance says a sunscreen without an expiration date should be considered expired three years after purchase, and that expired sunscreen should be discarded. If you do not know how old it is, discard it. For how sunscreen filters differ between markets, see our guide to Korean sunscreens.
How to make a product last its full life
- Keep it cool. The FDA warns that heat, such as a hot car, can make preservatives break down and let bacteria and fungi grow faster.
- Keep it dry. Moisture, such as a steamy bathroom, can make it easier for microbes to grow.
- Keep it clean. Wash your hands before dipping into a jar, and keep caps and applicators clean.
- Keep it yours. Do not share products. The FDA notes that store testers are even more likely to be contaminated than the same products at home.
- Date it. Write the opening date on the carton so the PAO number means something.
- Buy it new. The FDA warns that products resold online or at flea markets may be past their shelf life, used, diluted, or counterfeit.
Frequently asked questions
Does unopened skincare expire?
Yes, though more slowly. In the EU, a product that lasts 30 months or less must print a date of minimum durability. In the US, cosmetics need no date, and the manufacturer decides the shelf life. Storage still matters, since heat speeds up the breakdown of many actives and preservatives.
What does 12M mean on skincare?
It is the period after opening: 12 months from the day you first open the product. The open jar symbol comes from EU labeling rules, which require it on products that last longer than 30 months. The number is the brand's statement of how long the opened product stays safe to use.
Can you use expired skincare?
For sunscreen, no: the FDA says to discard expired sunscreen because it may no longer be safe and effective. For cosmetics, any date is the brand's own statement. A product past it may hold less of its active or a weaker preservative system. If its color, smell, or texture has changed, throw it out.
How long does sunscreen last?
Until its expiration date. FDA regulations require nonprescription drugs, sunscreen included, to carry one unless stability testing shows the product stays stable for at least three years. A sunscreen with no date should be considered expired three years after purchase.
Does vitamin C serum go bad faster than other products?
It is among the less stable actives. Reviews name stability as the main limit on vitamin C in cosmetics, and its breakdown depends on oxygen and pH. Keep it closed, cool, and out of light. Treat a clear change in color as a sign the formula has changed.
Does the PAO still apply if I barely used the product?
Yes. The period counts time since opening, not the amount used. Each opening lets in air, and each use can add microbes, whether you took a drop or a handful.
Related reading: Glass vial vs pump bottle, What is an ampoule?, Korean sunscreens.