An old lipstick changes in ways you can see and smell

The options around lipstick shelf life are set out side by side below, with the conditions that genuinely favour one over the other.

Why lipstick lasts longer than most makeup

Lipstick is anhydrous, meaning it contains essentially no water, so bacteria and moulds have little to grow in. That is why recommended periods after opening are usually measured in a year or more rather than in months. It does not make lipstick immortal, since the oils it contains oxidise over time regardless of microbes.

Waxes also change structure with repeated warming and cooling, which affects how the product applies. The failure modes are chemical and physical rather than microbial, which is why they look different from a spoiled cream.

The smell test

Rancid oils develop a distinctive stale, crayon-like or slightly sour smell that is easy to recognise once noticed. Because the product sits directly on the mouth, an off smell usually comes with an off taste as well. Any change from the original scent is a reasonable reason to discard, since there is no way to reverse oxidation.

Products containing more unsaturated plant oils tend to go this way sooner than those built on stable waxes. Storage in warm places accelerates the process considerably, which is why handbags and cars shorten lipstick life.

Bloom and texture changes

A white or greyish film on the surface of an old lipstick is usually wax that has migrated outward during temperature cycling. It is not mould, and wiping the top layer away generally reveals normal product beneath.

Hardening, crumbling and difficulty applying smoothly all indicate that the wax and oil structure has shifted. Colour can also shift slightly as pigments and oils age, particularly in lighter shades. None of these are dangerous, but they make the product unpleasant enough that replacement is usually the right call.

Contamination and the mouth

Every application transfers material from your lips to the bullet, including whatever was there at the time. Using a lipstick during an illness with cold sores or an oral infection risks reintroducing it later.

At the strengths actually sold, discarding products used during a cold sore outbreak is common advice and is sensible given how the virus persists. Sharing lipstick transfers organisms between people, which is why testers should be used with a disposable applicator.

Wiping the surface with a tissue before storing removes some contamination and costs nothing.

Storage that extends life

Cool, dark and dry is the entire principle, which means a drawer rather than a bathroom shelf or a sunny windowsill. Keeping the cap on properly prevents both dust and the slow evaporation of volatile components in some formulas. Avoiding repeated temperature cycling reduces bloom and texture changes more than anything else.

Liquid lipsticks dry out faster than bullets, since volatile solvents escape whenever the cap is imperfectly sealed. Owning fewer lipsticks and finishing them is the most effective preservation strategy available.

When to let go

Any change in smell, taste or texture is sufficient reason, regardless of how much product remains. The open jar symbol gives a tested period after opening, and lipsticks commonly carry a figure of a year or more.

On the ingredient list, a product that causes stinging or irritation it never previously caused should be discarded rather than persevered with. Persistent lip irritation across multiple products deserves a doctor's opinion rather than a bigger collection. Sentimental attachment to a discontinued shade is understandable and is not a reason to keep applying rancid oil.

Side by side

The takeaway

Smell it before you apply it, because rancid oil is the failure mode nobody looks for.

Skin changes slowly. Anything promising otherwise is selling the promise.