“Deodorant” and “antiperspirant” are often used interchangeably. This is for good reason, as they are often offered in the same product. But there are some important differences between them.
How does deodorant work?
Deodorants are used to suppress the often pungent smell associated with sweaty armpits. The smell is produced by bacteria that live on the skin and feed on fats and proteins secreted by the apocrine glands, a type of sweat gland.
These fats and proteins have no smell. But as the bacteria feed, they produce various byproducts, including propionic acid and butyric acid. It is these that lead to the unpleasant smell.
To fight these bacteria, deodorants contain two primary chemicals. The first is ethanol. Just like alcohol-based hand sanitizer, this kills many bacteria, reducing the harmful acids produced.
Supporting this are fragrances that mask the leftover scent – including that of ethanol.
While deodorants are good for suppressing the smell associated with sweaty armpits, they don’t deal with the sweat itself. This is where antiperspirants come into play.
How do antiperspirants work?
Sweat is about 98% water, with the remaining fraction made up of salts, including sodium, potassium, and calcium. It is pumped by another type of sweat gland called eccrine glands.
These long, twisted structures channel water from below to the surface of the skin when the body is under stress or is very hot.
Like the fats and proteins that ooze from the apocrine glands, sweat itself has no smell. But many choose to suppress sweat production, despite body odor having little to do with the liquid itself.
Antiperspirants contain aluminum salts, most commonly aluminum chloride hexahydrate. These can act in a number of ways to keep perspiration at bay.
They precipitate and form a jelly-like substance that “caps” the tip of the eccrine glands for a period. Salts can also travel through the glands and enter the cells lining the duct.
Thanks to osmosis, which is the movement of water to balance salt concentrations, the cells swell with liquid and block the eccrine passage.
Eventually, the aluminum salts are transported out of the cells and they return to normal, opening the duct again.
This is why antiperspirants need to be applied daily – and also why they cause yellow spots. Contrary to popular belief, yellow stains come from aluminum salts, not sweat itself.
By combining deodorant and antiperspirant, as many modern products do, we can fight body odor and sticky feeling at the same time.
the future of sweat
For some of us, these daily cleansing rituals can seem a little tiring – is there a better way?
According to recent research, those same bacteria that cause sweat smells — the skin’s microbiome — may also be the key to stopping those odors before they start.
We each have our own unique makeup of skin bacteria, which affect bad odors without deodorant or antiperspirant. This makes sense, because it’s bacteria that break down sweat molecules to create bad smells. In general, underarm microorganisms dominated by corynebacteria are associated with worse body odor.
Chris Callewaert, a researcher at the University of Ghent in Belgium, has been working for several years to understand the skin microbiome. In particular, he is testing whether we can treat body odor by transplanting bacteria from the armpit of a less smelly person to the armpit of a more smelly person.
First, the transplant recipient has to use antibacterial and antibiotic products to kill as many bacteria as possible in the current armpits and make room for the transplanted bacteria to move. donor armpit and applied to the recipient. While trials have been small so far — around 18 people — Callewaert’s website says the improvements in body odor are promising.
However, even if you can get past the gross factor, there are some downsides to the microbiome transplant approach. For example, there is a risk of transferring disease-causing microbes. Another strategy could be to create a healthy artificial skin bacterial community that can be cultured in the laboratory and standardized. Or we could try using bacteriophages – viruses that kill bacteria – to selectively remove the bacterial species that cause the worst odor.
Maybe one day we can stop using deodorant and antiperspirant and apply our ideal scent-free underarm skin microbiome.