Natural deodorant doesn't come with a loud expiration date stamped on the front, which leaves a lot of people wondering whether that half-used stick from two summers ago is still doing anything. Short answer: it does have a shelf life, and there are a few signs worth watching for.

Yes, it has a shelf life

Natural formulas are built on botanical oils and actives rather than the harsh synthetic preservatives that give conventional products their near-indefinite stability. That's a feature, not a flaw — but it does mean a natural stick is best used within a reasonable window. The figure to look for is the PAO symbol: the little open-jar icon on the packaging with a number like "12M" or "24M," meaning months after opening.

Signs it's past its prime

• The smell changed — oils can oxidize over time, shifting the scent.
• The texture or color shifted — graininess, separation, or hardening.
• It's just not performing like it used to, despite the same application.

None of these are dangerous, but they're your cue that the formula is no longer at its best.

How to make it last

Storage does most of the work. Keep your deodorant somewhere cool and dry, out of direct sun and away from heat. The two worst offenders are a hot car and a gym bag left to bake — heat can soften the stick and speed up the oils breaking down. A bathroom shelf away from the shower's heat, or a bedroom drawer, is ideal.

Zaffré sticks are a premium multi-month supply, so under normal use you'll work through one well within its window — just store it cool and dry and check the open-jar symbol on the packaging. MAX · SENSITIVE · Tea Tree.