Does dimethicone expire?

What if you mean pure dimethicone?

For a bottle of pure dimethicone, ask the supplier for the shelf life and storage instructions for that exact material. A moisturizer's or foundation's expiry period is not a substitute. For a finished cosmetic without clear shelf life information, contact the manufacturer rather than guessing from one ingredient.1

How do you know when to replace it?

1. 1Look for a printed expiry or best before date on the container and packaging. Follow the product's instructions.
2. 2Check for an open jar symbol with a number followed by M. The number tells you how many months the product should last after opening.
3. 3Write down when you first open the product so you can track that period.
4. 4Check for changes before continuing to use it. Poor storage can make a product deteriorate before its stated date.

US cosmetics do not have to display an expiry date, which is a labelling rule rather than a promise of immortality. In Europe, cosmetics with a lifespan longer than 30 months generally show a period after opening; those lasting fewer than 30 months show a best before date. Some products, such as single use packs, have exceptions.23

What changes mean you should throw it away?

Discard makeup that develops a bad smell, changes colour, separates, clumps, becomes unusually dry or runny, or feels different on your skin. Old makeup can irritate skin, and contamination with bacteria or mould can cause infection. A jar can still contain plenty of product when it needs replacing, so finishing it is not a compulsory assignment.4

The formula can change even when dimethicone remains on the ingredient list. Mixtures of water and oil can separate, products can dry out, and preservatives can break down over time. Dipping fingers into a container introduces microorganisms. Heat, air and sunlight can also change a cosmetic's smell, colour and texture.1

How should you store products containing dimethicone?

Keep cosmetics in a clean, dry place at room temperature, away from direct sunlight and heat. Close caps and lids securely after use, apply with clean hands or clean applicators, and do not dilute products with water. Bathroom moisture can encourage bacteria and fungi to grow, while a hot car can speed preservative breakdown.124

What if the product is a sunscreen?

Replace expired sunscreen even if it contains dimethicone and looks unchanged. The ingredients that provide sun protection can break down. If there is no expiry date, record the purchase date; sunscreen must maintain its original strength for three years. Replace it sooner if its smell, colour or consistency changes or it separates.4