How to store your skincare — shelf life, expiry, and stability.

Most skincare products have a shelf life that is shorter than people assume, and a degradation process that is quieter than the packaging suggests. An expired or destabilised product may not cause obvious harm — it may simply not work. For actives with a meaningful mechanism, that gap between purchase and application matters.

The Period After Opening symbol

European-market cosmetics and most international brands include the Period After Opening (PAO) symbol on packaging — a small open jar with a number inside (6M, 12M, 24M). This indicates how long the product remains safe and effective after the seal is first broken, assuming it has been stored correctly.

The PAO is distinct from the manufacture date or the best-before date on products that have not been opened. Unopened products generally have a longer useable life than the PAO would suggest. The PAO clock starts when you open the product.

Most serums: 6–12 months. Most moisturisers: 12 months. Sunscreen: 12 months (EU) or check the expiry date printed directly on the tube (US). Eye creams: 6–12 months. Cleansers: 12–24 months.

What degrades — and how to tell

Vitamin C (L-ascorbic acid). This is the active most prone to visible degradation. L-ascorbic acid oxidises in contact with air, heat, and light, converting into compounds with reduced efficacy. The visible sign is colour change: a fresh vitamin C serum is typically clear to pale yellow. As it oxidises, it deepens to orange, then brown. An orange-brown serum has not become dangerous, but its antioxidant and tyrosinase-inhibiting activity has diminished. More stable vitamin C derivatives (sodium ascorbyl phosphate, ascorbyl glucoside) are less susceptible to this, which is one practical argument for them over LAA.

Retinoids (retinol, retinaldehyde). Retinoids are photosensitive and heat-sensitive. Exposure to light and warmth accelerates breakdown. This is why retinol products are typically in opaque or amber packaging. A retinol that has been stored in direct sunlight or in a warm bathroom may lose potency before the product is used up.

Benzoyl peroxide. Benzoyl peroxide is an inherently unstable oxidising agent. It degrades with heat and age, which is why BP products often come with an expiry date rather than a PAO — the degradation timeline is more predictable. An expired BP product may have reduced antibacterial activity.

Products in jar packaging. Every time a jar is opened and fingers are dipped in, the entire product is exposed to air and introduces new microbes into the formula. Preservatives compensate for this, but jar packaging consistently shortens the practical shelf life of active-containing products relative to pumps or airless dispensers — particularly for vitamin C or retinol. This is not a packaging aesthetic criticism; it is a formulation stability concern.

Storage — what actually matters

The bathroom is not ideal. Steam and heat from showers cycle the product through temperature fluctuations repeatedly over months, degrading heat-sensitive actives. A bedroom shelf, a drawer in a cool room, or a skincare storage area away from steam is preferable — particularly for vitamin C and retinoids.

Direct sunlight accelerates degradation. A window ledge is the worst place to store anything with an active. UV and visible light both drive oxidation.

The fridge — useful but not always necessary. A cool environment slows oxidation in vitamin C products, particularly unstabilised L-ascorbic acid formulas. It is genuinely helpful for these. It is not necessary for most other products. Some oils may cloud in the cold (they clarify again at room temperature with no harm to efficacy). There is no benefit from refrigerating a cleanser, a SPF, or a well-formulated moisturiser in an airless pump.

Products without preservatives require refrigeration. Some brands formulate without preservative systems — typically marketed around this as a feature. These products genuinely need refrigeration and have a shorter post-opening life. The product will tell you.

When to discard

Colour change, separation of formula layers, altered smell, or change in texture beyond normal settling are each grounds to discard a product — even if the PAO has not expired. These indicate instability or contamination that a PAO cannot predict.

The most common practical loss from poor storage is efficacy, not harm. A degraded retinol will not cause a reaction; it will simply not produce results. For the cost of most active-containing serums, replacing a degraded product is the right decision.

The Lux & Glo niacinamide serum uses niacinamide — one of the most chemically stable skincare actives, resistant to heat and light degradation. The moisturiser uses squalane, shea butter, and avocado oil, all formulated with a full preservative system. Store both in a cool, dry place away from direct light, and they will remain stable through their expected product life.