We have all done it. Found a favourite lipstick at the bottom of a bag, a mascara that still has a little left, a foundation that was expensive and therefore feels too precious to throw away. It looks fine. It smells more or less fine. So we use it one more time.

That one more time is where the trouble starts.

Expired makeup is not really about a date printed on a pack. It is about what happens to a product once it has been opened, touched, shared, left in a hot bathroom, or forgotten for months.

Every time a wand goes back into a tube, every time a finger dips into a cream, a little bit of skin, oil, air and bacteria goes in with it. Fresh products are designed to cope with that, thanks to preservatives. Old products are not.

As preservatives break down, the formula itself starts to change. A foundation that once blended smoothly begins to separate or turn a shade more orange. A mascara that once coated evenly becomes dry and clumpy. A lip gloss changes colour. It is easy to blame your technique, or your skin, when really it is the product that has lost its integrity. The active ingredients have faded too. That SPF in your foundation will not protect you the way it once did, and a cream that promised hydration may now do little more than sit on the skin.

The bigger risk is invisible. An expired product can harbour bacteria, fungi and mould, even when it looks and smells completely normal. That is why the myth of the sniff test is so dangerous. Contamination does not always announce itself. On skin, it can show up as redness, itching, swelling, breakouts and clogged pores. Around the eyes, where the skin is thinner and far more sensitive, it can turn into styes or conjunctivitis. On lips, it can trigger cold sores. In rare cases, when applied to broken skin, it can lead to a far more serious infection.

Mascara and liquid eyeliner sit at the top of that risk list. The tube is dark, moist and warm, the perfect environment for bacteria to grow, and the wand reintroduces it with every use. Dermatologists generally advise replacing mascara after three months, even if the tube still feels full. Adding water or saliva to revive a dried-out tube only makes it worse, because it introduces new microorganisms and dilutes the very preservatives meant to keep the product safe. Sharing eye makeup, even with someone whose eyes look healthy, carries the same risk.

Powders do tend to last longer than liquids and creams, because bacteria love moisture. An eyeshadow or blush can often survive for up to two years if it is kept clean and dry. But longer does not mean forever. If the texture becomes hard, patchy or chalky, or the shade shifts, it has had its day. And natural or preservative-free products, despite their clean image, often expire faster, not slower, because there is nothing in the formula to hold back bacterial growth.

Then there is the little symbol most of us ignore. That tiny open jar with a number and an M — 6M, 12M, 24M — is the Period After Opening. It tells you how many months a product is meant to last after you first open it, not after you buy it. A 12M foundation opened last March is not meant to still be in use this March. Unopened products are more stable, usually for two to three years if stored in a cool, dry place, but heat, humidity and sunlight can shorten even that. A bathroom shelf, ironically, is one of the worst places to keep makeup.

None of this means every expired product will harm you. Many people use an old lipstick and feel nothing. But that is a gamble, not a guarantee, and the odds get worse the closer the product gets to your eyes, lips or broken skin.

The simplest habit is also the least glamorous one. When you open something new, write the date on it with a marker. Clean your brushes every week or so. Do not share eye and lip products. And when something smells off, looks off, separates, clumps or simply feels different from when you bought it, let it go. Replacing a mascara is far cheaper, and far less painful, than treating an infection it caused.

For more updates, join/follow our WhatsApp, Telegram and YouTube channels.