Magnesium and zinc sit side by side on natural deodorant labels like they're doing the same job. They're not. They work through two completely different mechanisms, and knowing which is which tells you a lot about how a formula will behave on your skin.
Zinc captures the odor molecules and holds onto them. Magnesium neutralizes the acids that are the smell.
Two different mechanisms, running alongside each other. Zinc is the engine; magnesium is a supporting layer.
Zinc chloride hydroxide works by adsorption. It captures and holds the odor molecules bacteria release, rather than covering them with a scent, with a secondary effect of limiting bacterial growth.
It's the active at the centre of every BioShield™ formula.
Magnesium hydroxide turns the acidic odor compounds into salts. Salts don't evaporate, so there's nothing left to reach your nose.
It barely dissolves, so it releases a little at a time as you sweat, and it does it without the harshness of baking soda.
What magnesium actually does
Magnesium has become a buzzword on deodorant labels, usually with no explanation of why it's there. Here's the real version: it isn't the primary thing stopping your odor, but it does more than the label lets on.
In a well-built natural deodorant it's a supporting active, a mild mineral that neutralizes the acidic compounds bacteria produce, right as they form. That's real odor work, a steady second layer. But it's support, not the engine.
Plenty of products marketed as “magnesium deodorant” lean on the word as if magnesium were doing all the heavy lifting. If it's genuinely working alone, it's carrying a load it wasn't built for, and that's often why those formulas fade.
Why the gentleness difference is real
Magnesium hydroxide is better tolerated than baking soda, and the reason is worth knowing, because it isn't the one usually given. It isn't that magnesium is “pH balanced,” because it isn't. A saturated solution of magnesium hydroxide actually reaches a higher pH than one of baking soda.
The difference is solubility. Baking soda dissolves readily in sweat, so essentially all of its alkalinity becomes available at once. Magnesium hydroxide barely dissolves at all, so it releases slowly and self-limits, going into solution only as acid arrives to consume it. Same reason magnesium hydroxide is the base used in antacids.
Which also means magnesium isn't inert. At a high enough loading it can still bother sensitive skin. Full breakdown in why deodorant burns.
Where Zaffré uses each
Core and Max both pair the zinc active with magnesium hydroxide. Sensitive is magnesium-free and uses triethyl citrate instead, working inside your skin's own acidity rather than raising it, which is why it suits sensitive skin, and why it's Dermatologist Tested.
Our fourth formula, Tea Tree, takes a botanical approach and doesn't run the BioShield system at all.
Which fits you? Use the buyer's guide, or see all four side by side on the comparison page.