What actually causes body odour
Fresh sweat is close to odourless. The smell most people are trying to avoid isn't the sweat itself — it's bacteria on the skin breaking that sweat down into smaller compounds, and those compounds are what you actually smell.
Sweat, then bacteria, then odour
Underarms carry apocrine sweat glands, which release a sweat rich in proteins and fatty compounds — different from the watery sweat on your back or forehead. On its own, this sweat has almost no smell.
The odour shows up once bacteria that live naturally on skin start metabolising that sweat, breaking it into byproducts your nose picks up immediately. More bacterial activity on more sweat means more odour — which is why the same amount of sweat can smell very different from one person, or one day, to the next.
Two different ways underarm products respond to this
Antiperspirants target the sweat itself — aluminium salts formulated to enter sweat ducts and temporarily plug them, so less sweat reaches the skin in the first place. Less sweat, in theory, leaves less for bacteria to work on.
Deodorants take the other route: leave the sweat alone, and work on the bacteria instead. If odour is what you're actually trying to solve, going after the bacteria addresses the direct cause, rather than trying to prevent the sweat that bacteria would otherwise feed on.
Where potassium alum fits
Potassium alum is a mineral astringent that sits on the surface of the skin, where it helps reduce the bacteria responsible for odour. It isn't entering sweat ducts and it isn't reducing how much you sweat — it's addressing the bacterial side of the equation directly.
That's the entire mechanism behind Phitcare's alum deodorant stick — one mineral, no added fragrance to mask anything, working on the bacteria rather than the sweat glands.
Habits that help alongside it
Washing underarms daily keeps the bacterial population lower to begin with, which gives any deodorant less to work against. Breathable fabrics — cotton over synthetics — let sweat evaporate rather than sitting against skin, which is exactly the environment bacteria prefer. And reapplying after a shower or a heavy-sweat stretch resets the surface rather than layering fresh mineral over old.
The short version
Odour comes from bacteria acting on sweat, not from the sweat itself. Solving it doesn't require blocking sweat glands — it requires managing the bacteria on the skin's surface, which is exactly what a single-mineral deodorant is built to do.