# What do cosmetic expiration symbols actually mean? Source: https://ingredientbeauty.com/blog/2026-10-15-cosmetic-expiration-symbols-meaning.html ## The open jar symbol, decoded The small open jar printed on many cosmetics carries a number and the letter M: 6M, 12M, 24M. It is the period after opening mark, common on products sold in Europe and increasingly used worldwide. It states how many months the manufacturer says the product remains suitable after you first open it, assuming normal storage. It is a guidance clock that starts when air and your fingers first meet the formula, not when you buy it. That distinction catches people out. A cream bought on sale and opened a year later starts its twelve months at opening, while a product opened at purchase and forgotten in a drawer has been counting down the whole time. Writing the opening month and year on the base with a marker is the unglamorous trick that makes the symbol actually usable. ## Other marks and real expiration dates Some products carry a true expiration date instead, printed as a date or a sand timer / hourglass symbol meaning use by the marked date whether opened or not. Sunscreen is the important case: its active filters degrade, regulators treat it as a drug in the United States, and an expired sunscreen cannot be trusted for its labeled SPF. Prescription and acne drug products likewise carry real dates that deserve respect. Most ordinary cosmetics in the United States are not required to show an expiration date at all, which is why the jar symbol and batch codes do the work. Batch or lot codes identify production runs for recalls; the string of letters and numbers that looks like a date but resists decoding is usually one of those, not a hidden expiry you failed to read. ## Which products actually go bad fastest Water based products used around the eyes are the high risk category: mascara is the classic three month product, because a warm, wet tube returned to a drawer daily is an excellent bacterial home, and liquid eyeliners share the problem. Cream products in jars you dip fingers into degrade faster than the same formula in a pump, purely through contamination each use adds. Sunscreen, vitamin C serums, and retinoid products fail by chemistry rather than contamination: actives oxidize and weaken, so an old product may be harmless but useless, which for sunscreen means unprotected while believing otherwise. Powders sit at the safe end, with little water for microbes; a powder can outlast its jar symbol by years if it looks, smells, and performs normally, though brushes need their own hygiene. ## Signs a product is finished, whatever the symbol says Trust direct evidence over printed guidance in both directions. A product is done if the smell turns sour, sharp, or like old crayons, if the texture separates and will not re mix, if the color has shifted noticeably, or if it stings skin it never stung before. Heat and sunlight accelerate all of this; the same cream lasts longer in a cool drawer than on a sunny bathroom shelf or in a car. Conversely, an unopened product stored cool and dark often remains fine beyond a conservative symbol, and brands know their marks err cautious. The judgment call is risk based: be strict with eye products, sunscreen, and anything applied to broken skin, and more relaxed with a powder blush or an unopened cleanser. Symbols inform that judgment; they do not replace it. ## Related reading If this topic is useful, these earlier guides go deeper on connected questions: [What does "water-resistant" on a sunscreen label actually mean?](https://ingredientbeauty.com/blog/2026-10-14-water-resistant-meaning.md), [What does "broad spectrum" on a sunscreen label actually mean?](https://ingredientbeauty.com/blog/2026-10-13-broad-spectrum-meaning.md), and [What does "oil-free" on a label actually mean?](https://ingredientbeauty.com/blog/2026-10-12-oil-free-meaning.md). ## Frequently asked questions ### What does 12M on a cosmetic jar mean? It is the period after opening symbol: the product is intended to be used within twelve months of first opening, assuming normal storage. The clock starts at opening, not purchase. Marking the opening date on the container with a pen makes the symbol practical, because nobody remembers when a jar was first opened a year later. ### Does sunscreen really expire? Yes, and it matters. Sunscreen actives degrade over time, and in the United States sunscreen is regulated as a drug with a printed expiration date. After that date the labeled SPF cannot be relied on. Sunscreen kept in heat, like a car or a beach bag all summer, can also degrade before its date, so storage matters as well. ### How long can I keep mascara? About three months after opening is the standard guidance, shorter if it dries, clumps, or smells off. Mascara wands return bacteria to a warm, wet tube daily and the product goes on lashes at the eye margin. It is the one cosmetic where the short timeline deserves to be taken literally rather than as a cautious suggestion. ### Can I use a product after its period after opening mark? Sometimes, with judgment. The mark is guidance with a safety margin, not a cliff edge. If an unopened or pump packaged product looks, smells, and feels unchanged, low risk products like cleansers and powders are commonly fine. Be strict in the other direction with eye products, sunscreen, and anything that has changed in smell, color, or texture, whatever the date says.