How does deodorant work? - New Style Motorsport

“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 key differences between them.

How does deodorant work?

Deodorants are used to suppress the often pungent odor associated with sweaty armpits. The odor 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 do not 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 combat these bacteria, deodorants contain two main chemicals. The first is ethanol. Like alcohol-based hand sanitizer, this kills many bacteria, thus reducing the harmful acids produced.

It is supported by fragrances that mask the scent that remains, including that of ethanol.

While deodorants are good at suppressing the odor associated with sweaty underarms, they don’t remove the sweat itself. This is where antiperspirants come into play.

How does deodorant work deodorants on a shelf
Credit: Chickadee Stock/Getty.

How do antiperspirants work?

Sweat is about 98% water, with the remaining fraction comprising salts including sodium, potassium, and calcium. It is pumped by another type of sweat gland called eccrine glands.

These long, twisted structures funnel water from below to the skin’s surface when the body is under stress or too hot.

Like the fats and proteins that ooze from the apocrine glands, sweat itself doesn’t smell. But many choose to suppress sweat production, even though body odor has little to do with the fluid itself.

Antiperspirants contain aluminum salts, most commonly aluminum chloride hexahydrate. These can act in a number of ways to keep sweating at bay.

They precipitate and form a gel-like substance that “plugs” the end of the eccrine glands for a period. The salts can also travel through the glands and enter the cells that line the duct.

Woman looking at sweaty armpit
Credit: Soda Ponchai/EyeEm/Getty.

Thanks to osmosis, which is the movement of water to balance salt concentrations, the cells swell with fluid and obstruct the eccrine passage.

Eventually, the aluminum salts are transported out of the cells and they shrink back to normal, opening the duct once more.

It is for this reason that antiperspirants should be applied daily, and also why they cause yellow staining. 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 combat body odor and stickiness at the same time.

The future of sweat

For some of us, these daily grooming rituals can seem a bit tiring. Is there a better way?

According to recent research, those same bacteria that cause sweat odors — your skin’s microbiome — may also hold the key to stopping those odors before they start.

Each of us has our own unique makeup of skin bacteria, which affects how bad we smell without deodorant or antiperspirant. This makes sense, because it is the bacteria that break down the molecules in sweat to create bad odours. In general, corynebacteria-dominated underarm microbes are associated with worse body odour.

Chris Callewaert, a researcher at Ghent University in Belgium, has been working for several years to understand the skin microbiome. In particular, he has been testing whether we can treat body odor by transplanting bacteria from the armpit of a person with less odor to the armpit of a person with more odor.

First, the transplant recipient has to use antibacterial products and antibiotics to kill as much of the bacteria in the armpit as possible and make room for the transplanted bacteria to move. Then, a sample of skin and bacteria shed from the donor’s armpit is collected and applied to the recipient. Although trials so far have been small (about 18 people), Callewaert’s website says improvements in body odor are promising.

However, even if you can get past the ick 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 an artificial healthy skin bacterial community that can be grown in the lab and standardized. Or we could consider the use of bacteriophages, viruses that kill bacteria, to selectively eliminate the bacterial species that cause the worst odour.

Maybe one day we can stop using deodorant and antiperspirant, and apply our ideal microbiome for odor-free skin to our underarms.

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