You turn over a moisturizer or foundation bottle and notice a tiny picture of an open jar. Beside it are a number and the letter M. Is that a manufacturing code, an expiration date, or something else?
The number tells you how many months the product is intended to remain suitable for use after you first open it. A 6M symbol means six months, 12M means 12 months, and 24M means 24 months.
This is called the period after opening, often shortened to PAO. It is useful information, but it needs to be read alongside storage directions, any printed expiration date, and the condition of the product.
A cream does not become dangerous at a precise midnight deadline. Equally, the symbol does not guarantee that a badly stored or contaminated product will stay suitable until that deadline.
Read the little jar this way
Look for a small container with its lid lifted, usually on the back, bottom, or side of the package.
| Mark beside the open jar | Meaning |
|---|---|
| 6M | Use within six months after first opening |
| 12M | Use within 12 months after first opening |
| 24M | Use within 24 months after first opening |
The letter M means months. It does not mean minutes, the manufacturing month, or the number of applications left.
For example, if you first open a cream marked 6M on March 10, plan to replace it around September 10. A 12M product opened that day reaches its stated period the following March.
These are calendar months, not accumulated days of use. Using the cream only on weekends does not pause the clock. Putting it away for a season does not restart it.
The symbol describes the product’s life after opening, not how long it should take to deliver a cosmetic result. A 12M face cream does not require 12 months of use before you can judge whether you like it.
Why opening matters
An unopened package and a product you use every morning have different histories.
Once you begin using it, fingers and applicators can introduce microorganisms. Exposure to air, moisture, light, and changing temperatures can also affect the formula.
Preservatives help control microbial growth, but they do not make a product permanently protected. Over time, a formula can dry out, change texture, or separate.
A jar of cream may therefore become unsuitable even though plenty remains inside. The amount left is not a measure of its condition.
Products also differ. A powder compact, a water-containing lotion, and a mascara tube do not necessarily have the same usable life. Follow the instructions for the particular product rather than borrowing the timeline from something beside it.
The opening date is different from the purchase date
For a PAO symbol, the relevant starting point is first opening the product for use.
Buying a cream in January and first opening it in April does not ordinarily mean that three months of its after-opening period have already passed.
But this does not make unopened cosmetics good indefinitely. Their unopened shelf life and storage history still matter.
Keep any carton that carries information missing from the container, or photograph it before recycling. If you bought an older product, inherited an unopened collection, or cannot establish its age, ask the manufacturer about its unopened shelf life.
Do not assume that an intact-looking lid proves a secondhand product has never been opened.
The easiest habit is to record the opening date immediately. Trying to reconstruct it months later from a holiday, haircut, or shopping receipt is much harder.
An expiration date is a different instruction
A printed date, such as “EXP” followed by a month and year, refers to a calendar deadline. The open-jar symbol gives a duration after opening.
Neither should be used to extend the other.
Suppose a product has a printed expiration date approaching in four months and an after-opening period of 12 months. Opening it today does not give you another full year beyond that printed date.
If both appear, follow whichever applicable limit comes first, along with the manufacturer’s directions.
A “best before” or minimum-durability date may also appear, especially on products labeled for European markets. Read the wording carefully rather than assuming every number on the package means the same thing.
A string of letters and numbers may simply be a batch identifier. It should not be treated as an expiration date unless the manufacturer identifies it that way.
Why some products have the symbol and others do not
In the United States, ordinary cosmetics generally are not required to carry an expiration date or a PAO symbol. Manufacturers are still responsible for product safety.
European labeling rules help explain why the open jar appears on many products sold here. Under those rules, products with a minimum durability longer than 30 months generally carry an after-opening indication, where that concept is relevant.
That does not mean a product marked 12M has a 12-month unopened life. Nor does it mean every cosmetic without the symbol is missing required U.S. information.
The period is product-specific. European regulators describe it as information supported by the product’s safety assessment and testing, rather than a random number chosen for the label.
If you cannot find a symbol, check the carton and the manufacturer’s instructions. Contact customer service if the usable period remains unclear.
Avoid relying entirely on an online batch-code calculator. Ask the brand to interpret its own code when age or labeling is uncertain.
Sunscreen needs its own check
A moisturizer or foundation with SPF deserves special attention. In the United States, sunscreen products are regulated as drugs; an SPF-containing cosmetic can be both a cosmetic and a drug.
Do not use an open-jar symbol as permission to keep using expired sunscreen.
Follow the sunscreen’s expiration date. FDA guidance says sunscreen without an expiration date should be considered expired three years after purchase.
Writing the purchase date on an undated sunscreen helps you keep track. If you cannot establish that it was bought within the last three years, replace it.
Storage matters here, too. Leaving sunscreen in a hot car can damage the product before its printed deadline.
Acne treatments and other medicated products may also have instructions that differ from ordinary cosmetics. Check their drug labeling, and ask a pharmacist if you are unsure which date applies.
Replace a changed product sooner
You do not have to finish the stated period if something has changed.
Reasons to stop using a product include:
- A new unpleasant or unusual odor.
- A noticeable, unexpected color change.
- New clumps, grittiness, drying, or crumbling.
- A change from its usual consistency to something runny or separated.
- Visible mold or other apparent contamination.
- New irritation when you apply it.
Judge changes against the product’s normal appearance. Some formulas intentionally separate and direct you to shake them before use. That is different from a previously smooth cream developing an unexplained new layer.
Do not keep applying a questionable product to see whether it still “works.” And do not scrape off visible mold and use what remains.
Looking and smelling normal does not prove that a product is free from harmful microorganisms. Appearance is an additional check, not a reason to ignore the recommended replacement period.
Give eye makeup extra attention
Mascara and liquid eyeliner warrant particular care because they are used close to the eyes.
The American Academy of Dermatology recommends replacing mascara after three months. Follow a shorter product-specific instruction if one is provided.
Do not wait until a tube is empty. Occasional use does not make an old mascara permanently suitable.
If it dries out, discard it. Adding water or saliva can introduce microorganisms and interfere with the preservative system.
Do not share eye cosmetics. If you develop an eye infection, stop using eye-area makeup and discard the eye cosmetics you were using when the infection occurred.
A long period on a face cream is not a guide for mascara. Each product needs its own decision.
Store products where their labels expect them to live
A clean, dry location at ordinary room temperature, away from direct sunlight, is a sensible choice unless the manufacturer says otherwise.
A drawer or cabinet away from heat may be more suitable than a sunny windowsill or a damp shower ledge.
Close caps and lids securely after use. Keep container openings clean, and avoid leaving products uncapped while you finish the rest of your routine.
Do not leave your makeup bag in a hot vehicle. Warm, damp conditions can favor microbial growth, while heat can affect preservation.
Refrigeration is not a way to reset the opening date or rescue a deteriorated cream. Follow the product’s storage instructions rather than assuming colder always means better.
The stated period depends on appropriate storage and handling. It is not protection against every condition a product might encounter.
Clean hands and applicators still matter
Start with clean hands, especially when you need to dip into a jar. Keep any applicator used with the product clean.
A clean spatula may help you avoid dipping fingers into a cream, but it needs cleaning, too. It does not extend the labeled period.
For makeup brushes, dermatologists recommend washing every seven to 10 days.
A straightforward brush-cleaning routine is:
- Rinse the bristle tips under lukewarm running water.
- Wash the tips with gentle shampoo and water, working out accumulated makeup.
- Rinse until the water runs clear.
- Gently squeeze out excess moisture with a clean towel.
- Lay the brushes flat to dry, with the tips extending over the counter’s edge.
Avoid soaking the entire brush head and handle, which can loosen the glue.
Follow the cleaning directions for reusable sponges and other tools. Let them dry before storage rather than sealing them away damp.
Cleaning tools supports safer use. It does not make an expired or contaminated cosmetic suitable again.
Be cautious with “natural” and homemade products
Words such as “natural” do not tell you how long a product will remain suitable after opening.
The important questions are how the formula is preserved, how it was made, how it is packaged, and what directions the manufacturer provides.
Do not assume that avoiding preservatives automatically makes a product safer. An ineffective preservation system can allow microorganisms to grow.
Also avoid adding water, herbal tea, oils, or other ingredients to a finished cream to stretch it or change its texture. The original instructions were written for the original formula.
A homemade mixture does not acquire a reliable shelf life because you put it into an old container marked 12M. That symbol belonged to the manufacturer’s product.
What if you cannot remember when you opened it?
First, look for a dated photo, receipt, or note that may help establish the timeline. A receipt shows purchase, however, not necessarily opening.
If the date remains uncertain, consider the product’s type and history. Be particularly cautious with old eye makeup and sunscreen.
A half-used product discovered at the back of a drawer after several years is not a good candidate for guessing generously.
For an unopened product of uncertain age, ask the manufacturer before assuming it is usable. For a long-opened product with an unknown history, replacement is usually the more practical choice.
Avoid giving questionable products to someone else simply because you do not want to waste them.
Make the next decision easier
You do not need a complicated inventory. A few habits can prevent uncertainty:
- Write “opened” and the date on the container with a permanent marker or small label.
- Record the replacement month beside it.
- Photograph the label if the directions are on a disposable carton.
- Open one similar product at a time when practical.
- Choose smaller sizes if you rarely finish larger containers within their stated periods.
Keep writing clear of ingredient lists, warnings, and printed dates.
These steps help you use what you buy without treating every unfinished bottle as something you must keep.
If a product causes a reaction
Stop using it rather than assuming a reaction is harmless because the opening period has not ended.
A fresh product can irritate your skin or cause an allergic reaction, too. The PAO symbol cannot predict individual tolerance.
Seek medical advice for persistent or worsening redness, swelling, burning, or a rash. Eye pain, light sensitivity, or changes in vision warrant prompt medical attention.
Keep the packaging and batch information if you need to identify the product when speaking with a clinician or manufacturer.
The useful takeaway
The open jar is a simple reminder: 6M, 12M, and 24M mean months after first opening.
Record the date, follow any earlier expiration deadline, and store the product as directed. Replace it sooner if its condition changes or contamination is suspected.
The goal is not to empty every container. It is to know what you are using—and when it is time to let it go.
Wondering when something’s still safe to use – or when it’s time to toss it? Check out how to handle mold on cheese and the rules for refreezing thawed meat.
