"Deodorant" and "antiperspirant" get used interchangeably, but they're two different products that work in completely different ways. Understanding the difference is the first step in deciding what you actually want to put under your arms every day.
How antiperspirants work
Antiperspirants use aluminium-based compounds (like aluminium chlorohydrate or aluminium zirconium salts) that dissolve in sweat and form temporary plugs in your sweat ducts. Less sweat reaches the surface of your skin, so there's less moisture — and less material for odour-causing bacteria to break down. In short: antiperspirants stop sweat.
How deodorants work
Deodorants don't stop you sweating. Instead, they target the odour — either by neutralising or inhibiting the bacteria that cause it, or by masking it with fragrance (or both). Your body continues to sweat normally, which matters because sweating is one of the ways your body regulates temperature.
What does "aluminium-free" actually mean?
An aluminium-free deodorant simply contains no aluminium compounds — which means it cannot and does not block your sweat glands. Any product labelled "natural deodorant" should be aluminium-free by definition, because blocking sweat is the one job aluminium performs in this category.
To be clear and honest about the science: regulators and major health bodies have not established that the aluminium in antiperspirants causes serious disease, and you'll find conflicting headlines on both sides. For many people, the decision to go aluminium-free isn't about fear — it's about preference: letting the body sweat as it's designed to, avoiding a mechanism that plugs pores, and choosing simpler ingredient lists they can understand. That's the philosophy Si:zen is built on: support your body's natural processes rather than disrupt them.
So how does a natural deodorant control odour without aluminium?
The effective ones use ingredients that change the underarm environment so odour-causing bacteria can't thrive. Common approaches include:
- Magnesium hydroxide — raises the pH at the skin's surface just enough to make it inhospitable to odour-causing bacteria, without blocking sweat. This is the active approach in Si:zen, chosen because it's effective and gentle on sensitive skin.
- Bicarb soda (baking soda) — effective against odour, but a well-known irritant for many people, causing redness, itching and rash with daily use.
- Zinc compounds — neutralise odour molecules directly.
- Fragrance-only formulas — these mask odour rather than address it, and are usually the products that give natural deodorant a bad name.
Which should you choose?
It depends on what you're trying to achieve:
- If your priority is staying as dry as possible — for example, for a presentation or a wedding day — an antiperspirant is the product designed for that.
- If your priority is odour control while sweating naturally, with simpler ingredients and less risk of irritation, an aluminium-free natural deodorant is the better fit.
- If you have sensitive skin, look specifically for a bicarb-free natural formula — this is the single biggest factor in whether natural deodorant irritates you.
Frequently asked questions
Is deodorant or antiperspirant better?
Neither is universally better — they do different jobs. Antiperspirant reduces wetness; deodorant controls odour. The right choice depends on your priorities, your skin and your lifestyle.
Will I sweat more with an aluminium-free deodorant?
You'll sweat your normal amount — which can feel like more if you're used to antiperspirant blocking it. Most people adjust within a couple of weeks. We've covered this in detail in our guide to the natural deodorant transition period.
Are natural deodorants effective?
Well-formulated ones are. The key is the active ingredient — look for something that neutralises odour-causing bacteria (like magnesium hydroxide) rather than a formula that only adds fragrance.
Aluminium-free deodorant vs antiperspirant: what's actually different?
The core difference is simple: antiperspirant blocks sweat with aluminium compounds, while aluminium-free deodorant lets you sweat normally and instead targets the odour-causing bacteria. Neither is universally "better" — it depends on whether your priority is stopping sweat or controlling odour naturally.
What's in Si:zen's natural deodorant?
Sunflower oil, magnesium hydroxide, isoamyl laurate, beeswax, cetearyl alcohol, hydrogenated vegetable oil, triethyl citrate, Vitamin E and fragrance (parfum) — see our Fragrance FAQ for details. Nine ingredients you can understand — no aluminium, no parabens, no bicarb. See the full details on the product page.