Does Skincare Expire? How to Store What You Already Own

You have a shelf, or a drawer, or a bag under the sink. Somewhere in it: a vitamin C serum gone the color of weak tea, a sunscreen from a vacation you can date by the photographs, and a retinol you bought on a recommendation and stopped using in week two. Most of it is still there because throwing away something expensive feels like the waste — when the waste already happened.

This is the least glamorous page on this site and probably the one that saves you the most money. None of it requires buying anything.

Air, light and heat — that is the whole list

Almost everything that goes off does it for one of three reasons, usually all three at once.

• •Air. Oxygen breaks down the two ingredients most worth having — vitamin C and retinoids. Every time a pot is opened, the whole surface meets air again.
• •Light. Retinoids in particular are broken down by daylight. A clear bottle on a windowsill is a slow way of throwing money away.
• •Heat. Heat speeds up everything above, and it is why the room you almost certainly keep all of this in is the wrong one.

The bathroom is the worst room in the house

A bathroom is hot, steamy and bright — three for three. Ten minutes of shower steam twice a day, for a year, is a real amount of accelerated aging for something that cost you sixty dollars.

Almost anywhere else is better: a bedroom drawer, a linen closet, a cupboard away from the radiator. Cool, dark, dry, and no less convenient than a cabinet over a sink. If you will only keep up a routine with the products in front of you, then compromise — leave the cleanser and the moisturizer where they are, and move the actives somewhere dark.

What the little open-jar symbol means

Turn a product over and you may find a small icon of an opened jar with something like 12M or 6M next to it. That is the period after opening: how long the manufacturer expects it to be good once you have opened it — not how long it keeps sitting sealed in a cupboard. A 6M serum you opened last February is out of date whatever the box says.

If there is no symbol and no date, a working rule most people can live with: about a year for anything with an active in it, two for a plain cleanser or moisturizer, three months for anything that goes near your eye.

The color change that means stop

The most common expensive mistake on a shelf is a vitamin C serum that has turned. Fresh L-ascorbic acid is clear or very pale. As it oxidizes it goes yellow, then orange, then brown — and by then it is not doing what you bought it for, and the breakdown product can be mildly irritating on skin that is already reactive.

There is no rescuing it. If it is orange, it is finished. Two things make it last: buy the smallest bottle you will actually finish, and keep it cool and dark — this is the one product a refrigerator genuinely suits. And if you keep buying them and keep watching them turn, a stable derivative holds up far better in a warm room; the labels say things like ascorbyl glucoside or tetrahexyldecyl ascorbate. A gentler serum still working in month four beats a stronger one that died in month two.

The refrigerator is a tool, not a rule

"Keep your skincare in the fridge" gets repeated a great deal and it is only sometimes right. A vitamin C serum: yes. A gel eye product you like cold: fine, and it feels lovely on a bad morning.

Almost everything else: no. Rich creams, oils and balms are emulsions, and cold can thicken them, separate them, or break them so they never come back together. Clay masks go gritty. And moving something in and out of the cold over and over is harder on it than leaving it at a steady room temperature. Cool, dark and steady is the goal, and a cupboard achieves all three.

Retinoids: a tube, not a pot

Retinoids are worth the trouble, and they are the fussiest thing you own. Two rules and you are done.

• •Buy it in an opaque tube or an airless pump, not a wide open jar. A jar exposes the whole surface to air, and to your fingers, every single night.
• •Keep it dark and away from heat. Not the windowsill, not the car, not the shelf above the radiator.

Encapsulated retinol — the label will tell you — is built to survive more of this, and is a sensible choice if the bathroom is the only place you will remember to use it. And do not decant a retinoid or an acid into a travel bottle to save space: you will not know what the bottle is made of, whether it is airtight, or whether the preservative system still works in it. Take the tube.

One more, because it is the pairing people get wrong: keep benzoyl peroxide and a retinoid in separate applications — one in the morning, the other at night. That is the same advice as using more than one active, and it is the safe answer whichever formulation you have.

Sunscreen is the one where the date really matters

Sunscreen is regulated as a drug in the United States, and it either carries an expiration date or has been shown to hold up for three years. So: if there is a date, believe it. If there is not, count three years from when you bought it.

More important than the date is where it has been. A bottle that spent July in a car, or in the sun at the bottom of a beach bag, has been cooked — and heat degrades the filters. If it is grainy, watery, separated, or smells different from new, it is not protecting you at the number on the front. This is the one product on the shelf where quietly getting less than you think has a consequence you will still be able to see in ten years.

Six things that mean throw it out

• •The color changed — especially clear or white turning yellow, orange or brown.
• •The smell changed, or it now smells of crayons or old cooking oil.
• •It separated and will not go back together when you shake it.
• •The texture changed: grainy, watery, tacky, or suddenly much thicker.
• •It stings on skin where it never used to.
• •Anything you put near your eye that you opened more than three months ago.

Habits that shorten a product's life without your noticing

• •Water and fingers. Do not add water to thin something out, do not top a bottle up, and do not share. Each of those introduces something the preservative then has to fight.
• •Buying big. A large bottle of an active is worse value than a small one you finish while it still works.
• •Leaving it in the car. A car in summer reaches temperatures nothing on this list survives.
• •Leaving the lid off. On a product with vitamin C or a retinoid in it, the lid is not decoration.

When it is not the product that changed

Sometimes something you used happily for two years starts stinging and there is nothing wrong with it — your skin changed. That is ordinary in perimenopause and after: a thinner, drier barrier reacts to things it used to tolerate without complaint. The tell is whether the product looks and smells normal. If it does, and it still stings, the answer is a gentler routine rather than another bottle of the same thing.

And if something is genuinely sore, spreading, swelling, or not settling within a few days of stopping, see a doctor rather than working down the shelf hunting for the culprit.

The part that is actually worth money

Hardly anybody has a product problem. Most women have a too many products, half of them dead problem: several actives quietly fighting each other, and two or three that stopped working months ago. Clearing out what has turned, and moving three bottles out of the steam, costs nothing and will do more for your skin than the next thing you buy.

Start there. Then whatever is left has a fair chance of working.