Use-by, best-before and PAO explained

The date on the packaging is the piece of information people think about least yet decide with most: it gets checked while clearing the fridge, while picking from the discount shelf, while tidying the make-up bag. The trouble is that there is no single 'date'. Food carries two different types of date, cosmetics add a period of use after opening alongside a date, and the three make different promises. Anyone who can tell those three promises apart avoids both needless waste and needless risk.

Even the way the date is written carries information

In food, how precisely the date is written gives away how durable the product is. Products with a shelf life shorter than three months show the day and month, those between three and eighteen months need only the month and year, and products lasting longer than eighteen months may show the year alone. So someone who sees only a year knows they are holding a very durable product. Also, if a storage condition is printed next to the date, the promise is tied to that condition: a product that should be kept refrigerated but was left at room temperature no longer has a valid assurance on its label.

Three labels, three different promises

The rule changes the moment the pack is opened

The date on the pack is a promise made for an unopened product. The moment you open it, that promise gives way to a second rule. In food this rule is usually printed in a corner of the label: 'once opened, keep refrigerated and consume within three days', for instance. That sentence overrides the distant date on the lid; a jar of tomato paste with a month of life left will not last until that distant date once opened. The logic is the same in cosmetics: the period in the open-jar symbol runs from the day you open it, not from the date of manufacture. A marking such as '12M' inside the symbol tells you how many months the product should be used within once opened. So a cream that sat unopened in a cupboard for two years starts a fresh period on the day it is opened.

Not every cosmetic carries a PAO symbol

On some products you will not find the open-jar symbol at all, and that is not an omission. Cosmetics with a shelf life longer than 30 months may carry no separate date either; that does not mean they last forever, as the open-jar period still starts on the day you open it. On single-use products (single-dose ampoules, single-use masks) there is no point in defining a period after opening. It may also be unnecessary on airtight, pressurised or non-reclosable packaging (such as aerosol-type products). Some product types where a risk of deterioration does not arise in practice fall into the same category. On the other hand, it makes sense to look for the symbol on products that contain water and are touched by hand or brush: eye-area products, creams, cleansers and liquid foundations lead that group.

Spotting deterioration before you can see it

• In serums containing vitamin C, a shift in colour from yellow to orange and then brown is a known sign that potency is falling.
• Components sensitive to light and air such as retinol are sold in dark, airtight packaging; if the pack has been left open, keeping the period shorter is sensible.
• In products containing plant oils, a bitter, paint-like smell is the herald of oxidation.
• In emulsions, separation of the watery and oily phases, a texture turning watery or forming lumps, shows the formula is tiring.
• In food, a bulging lid, the absence of the expected 'pop' when a jar opens, cloudy brine and thick ice crystals in a frozen product are warning signs.
• If a tin shows rust, a dent or a leak, it is right not to use it whatever the date says.

Batch codes and recalls

The batch (lot) number marks a group of products made under the same conditions. When a problem emerges, recall announcements are made through this number; that is, not every product of a brand is called back but only the batch concerned. In Türkiye, food-related announcements are published by the Ministry of Agriculture and Forestry, while notices about cosmetic products come from the Turkish Medicines and Medical Devices Agency. The practical benefit for you is this: keeping the box of an expensive or long-lasting product, together with its date and batch details, for as long as you use it makes both PAO tracking and matching against a possible announcement possible.

Storage conditions can void the date

A date is given on the assumption that the product is stored correctly. A product whose cold chain has been broken can spoil earlier despite its date, and the time it takes to get home from the top shelf of a supermarket chiller counts in that sum too. In cosmetics the commonest mistake is keeping products in the bathroom: swings in temperature and humidity shorten the life of products with active ingredients in particular. Sunscreen forgotten in a glovebox or a boot is a similar example, because in summer the temperature inside a car can rise far above the range the formula was designed for. Cool, dry and dark storage is the condition that genuinely keeps a date alive in both worlds. Even inside the fridge the position matters: the door shelf sees the widest temperature swings, so the inner shelves are a better address for items such as milk and eggs. By the same logic, the best place for cosmetics is a closed drawer away from radiators and windows.

Typical windows in food once opened

The gap between the date on an unopened product and the window of an opened one is where both waste and risk gather most in the kitchen. The general tendency runs like this: pasteurised milk and fresh juice keep for a few days in the fridge once opened, the contents of an opened tin should be moved out of the metal into a glass or plastic container and used up equally quickly, and dense products such as tomato paste keep a little longer under a thin film of oil. With dried pulses and pasta, opening does not shorten life noticeably, and the real task is protecting them from moisture and pests. The definitive period is always in the 'once opened' instruction on the pack; where there is no instruction, the product's water content and storage conditions guide you.

Product life in the make-up bag

• Mascara and liquid eyeliner: because they touch the eye area and take in air at every use, they have the shortest window.
• Liquid and cream foundation: those in pumps or tubes cope more easily than those in jars you dip a finger into.
• Powder products (face powder, blusher, eyeshadow): they last longer as they contain no water, and the real issue is the oil and microbes carried in on brushes.
• Lipstick and lip gloss: they touch the lips directly, so replacing them after a period of illness is sensible.
• Pencil products: they have a relative advantage because sharpening refreshes the surface each time.
• Brushes and sponges: not products but part of the system; unless washed regularly they will contaminate even the cleanest product.

A simple date system at home

• Put the nearest dates at the front of the cupboard and the furthest at the back; whatever you buy goes behind.
• Write the month you opened a cosmetic on a small label on the cap rather than trusting your memory.
• Set aside a 'use these first' shelf in the fridge and gather opened items there.
• Write what it is and the date on anything you put in the freezer; once it frosts over it becomes hard to identify.
• A five-minute review once a month heads off most of the waste before it happens.

The real benefit of this order is not rescuing individual items but reducing the number of decisions you have to make. Someone who knows what was opened when does not have to sniff and guess every time: they are relaxed with products carrying a quality date and apply the rule without hesitation on those carrying a safety date.

Near-date products on the discount shelf

Supermarkets may gather products approaching their date in a discounted section, and used properly that is a good opportunity for both budget and waste. Two questions settle the decision: which type of date does this product carry, and when will I actually use it. A few days' window causes no trouble on a durable product; on a perishable one the same window narrows further with the journey home. There is also the freezer option: freezing a freezable product before its date runs out extends the window, but freezing it after the date has passed does not undo the past. The same logic applies to buying cosmetics on multibuy offers; the third of three units can wait as long as it stays unopened, but on the day it is opened it starts a period of its own.

Then there are the cases where no date can be read at all: the ink on the pack has rubbed off, the print has run in the damp of the fridge, or the product has been taken out of its original box. If you cannot remember the item's story in such a case, looking at what kind of product you are holding is a firmer route than guessing: with a perishable food the uncertainty is reason enough on its own, while with a durable product the condition of the packaging and the contents settles it. When the same uncertainty arises in cosmetics, the first measure to reach for is the product's smell and texture; if both are normal, setting a short window of use and sticking to it is sensible.

A 30-second check at the shelf

• First work out which type of date you are looking at: a safety date or a quality date.
• Estimate when you will actually use the product and compare the date with that estimate; a discount does not mean you will get through it quickly.
• If you are buying from the chiller, leave the product to the end of your basket and account for the journey home.
• In cosmetics, look for the open-jar symbol on the back of the box and compare the period with how often you use it.
• Look at the packaging itself: leave it on the shelf if there is bulging, leakage, a broken seal or a damaged cap.

Common mistakes

• Deciding a perishable product is safe by smelling and tasting it; some risks give off neither smell nor taste.
• Binning a durable product untouched because its date passed a day ago.
• Trying to rescue an out-of-date food by freezing it; freezing pauses the process, it does not reverse it.
• Not noting the month of opening a cosmetic and leaving the PAO period to memory.
• Realising after throwing the box away that no date or batch information is left on the product.

Who does this matter for?

The habit of reading dates changes outcomes directly for some groups. In homes with babies the window is narrow for opened items such as milk and purees, and following the label is the most practical assurance. For people with suppressed immunity, pregnant women and older people, following dates on perishable food matters even more; in this group the doctor's advice is what guides the decision. For households that shop in bulk and keep stock, the main gain is less waste: arranging the cupboard by date quickly cuts the number of items forgotten at the back. For people who collect make-up the issue concentrates around the eyes, because products used there both touch directly and are opened often. This article is general information; if discomfort follows a food or a cosmetic, a doctor should be consulted.

Planning shopping around dates starts while you write the list, and we covered that more broadly in our supermarket shopping guide. If you are curious about what is in the product in your hand you can scan it to see the breakdown, and study what individual substances do on our Discover page.