How do deodorants keep you from stinking?


The underarm industry has evolved into a multibillion-dollar business in the U.S.“The underarm industry has evolved into a multibillion-dollar business in the U.S.© Kimberly White/Corbis

The inventor, his name lost to history, found himself at the intersection of Stinky and Smelly streets in the City of Brotherly Love. He stood at the crossroad and pondered the age-old dilemma of body odor. What could make a person smell better, he intoned? It was 1888, the height of the Industrial Revolution, and Philadelphia, like most communities, was brimming with the ripe.

The inventor, nicknamed "Mum," knew there had to be a better way to make people smell more pleasant. Humans had tried for centuries with varying degrees of success to mask the nose-wrenching scents emanating from their soiled and sweaty bodies. The ancient Egyptians preferred perfumed oils or cinnamon, which they rubbed under their arms. In Asia, the odoriferous slathered their armpits with a mixture of rock salt. The ancient Greeks scraped their underarms with a sharp metal tool, hoping to chisel the smell off [sources: MUM, Lewis].

Such tricks of alchemy wouldn’t do, Mum thought. Science needed to find a better way. So, in a laboratory, kitchen or basement somewhere on the banks of the Schuylkill River, Mum mixed a creamy wax of zinc oxide. When he was finished, the first deodorant was born. Mum trademarked his concoction, and it soon went on sale in small tins. People applied the cream liberally to their underarms and feet. Women even used the substance, henceforth named MUM, during menstruation. MUM wasn’t a big seller because it was messy and hard to apply [sources: MUM, Newman].

Yet, Mum was a pioneer. A few years later, people began swiping on the first antiperspirants to combat their underarm odor. Problems were many. Their acidity caused skin irritation. They discolored blouses and shirts. Better antiperspirants were invented. Today in the United States, the antiperspirant and deodorant industry is a multibillion-dollar business, each brand bursting with a variety of ingredients that helps wipe the stink away [sources: Poucher, MUM, Newman].

Underarm Science

We all sweat. It’s our body’s way of cooling us down. Sweat doesn’t stink, yet we do. Why is that? The zinc oxide Mum used suggests that the 19th-century inventor knew that bacteria, not perspiration itself, made underarms reek. Zinc oxide is an antibacterial. Bacteria were relatively new concepts at the time, which makes Mum’s reasoning (if he so reasoned) more than amazing. Since then, scientists have figured out that bacteria feeds on some of the substances in sweat, thereby causing our bodies to smell. Your underarms are ground zero.

Underarms brim with apocrine glands, one of two main types of sweat glands that cover your body. Usually found in areas laden with hair follicles, apocrine glands produce a milky perspiration comprising water, proteins, lipids, fatty acids, cholesterols and iron-containing salts. When you perspire, the walls of the apocrine glands shrink, allowing the fluid to glom onto your hair follicles. The perspiration, which at this point is odorless, eventually pushes its way to the surface of the skin, escaping through the tiny openings of the hair follicles. Bacteria take notice and begin devouring the protein and fatty acids in the sweat. The stench is the result of bacterial breakdown [source: Mayo Clinic].

Deodorants and antiperspirants are the first line of defense against body odor (as is taking a shower and bath), yet don’t get the two confused. Although we use the names interchangeably, each has its own method of dealing with body odor. The chemicals in antiperspirants, such as aluminum chloride or aluminum hydroxybromide, keep you from sweating. They permeate the cells that line the ducts of the sweat glands near the epidermis, the top layer of the skin. The chemicals and water are then drawn down into the cells, causing the sweat ducts to swell and become obstructed. That prevents some perspiration from migrating to the surface of the skin. The less you sweat, the less food there is for bacteria to devour. Hence, the less you smell [source: Poucher].

A Cup A Day

The average person sweats nearly four cups of water a day, although we can sweat up to 40 cups [source: Goodman].]

The Killing Pits

Deodorants, however, don’t stop you from sweating. Instead, deodorants use antimicrobials to kill bacteria and slow their growth. Bacteria crowd under your arms, with 1 million of the tiny creatures living on every square centimeter or so of skin. Although a deodorant can never be an antiperspirant, an antiperspirant can be a deodorant. That’s because some antiperspirants have antimicrobial ingredients [sources: Poucher, Antiperspirants Info].

One of the main ingredients is triclosan, a common biocide that is also found in plastics, textiles, toothpaste, antibacterial soaps, cosmetics and body washes. Triclosan takes aim at the cell wall of the bacteria, killing the smelly beasts [source: U.S. FDA, Antiperspirants Info].

Although the U.S. Food and Drug Administration says triclosan is not harmful to humans, some studies indicate that the chemical alters the regulation of hormones in animals. Other studies suggest the chemical helps make bacteria resistant to antibiotics [source: U.S. FDA, Yazdankha et al.].

Polyhexamethylene biguanide is another active ingredient in deodorants. PHMB, as it is called, is an effective bacteria killer and is often used as a disinfectant in swimming pools and hot tubs. It does a good job of wiping out bacteria that cause adenovirus ocular infections. Moreover, alcohol, another ingredient, is also effective at killing bacteria [source: Antiperspirants Info, Romanowski et al.].

Still, do we really need deodorants and antiperspirants? Some people apparently don’t. Researchers at the University of Bristol in Great Britain found that 75 percent of people they studied had a particular version of a gene that doesn’t produce underarm odor. Nevertheless, these people used deodorants and antiperspirants. Moreover, those with the gene variation didn’t have sticky ear wax, which apparently is a good indication of whether someone’s armpits smell [source: Science Daily].

Keep reading for a plethora of information on your underarms.

Lots More Information

Author’s Note: How do deodorants keep you from stinking?

As a writer of history and a student of science, personal hygiene through the ages has always intrigued me. I can’t watch a period movie, such as "Pride and Prejudice," or a TV series, such as "Game of Thrones," without wondering what people smelled like under their perfumed wigs or armor. Sansa Stark and Daenerys Targaryen might look beautiful on TV, but if they lived during the time of the Seven Kingdoms, they probably smelled like rotten dragon eggs. While the Romans spent countless hours in bathhouses, medieval knights and princesses wanted nothing to do with taking a bath. In fact, for centuries the people of Europe did almost everything they could to stay dirty. They "washed" their hair with powder and then combed it out. If they did bathe, it was once a year. We’ve come a long way, thank goodness. For the record, I just showered and slathered my stick deodorant under both pits.

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  • Antiperspirants Info. "Antiperspirants & Deodorants." (May 15, 2014)
  • Goodman, Brian. "Deodorant Scientists Arm Against Odor." June 22, 2006. (May 15, 2014)
  • Lewis, Kristin. "The History of Stink." Scope. Nov. 12, 2012. (May 15, 2014)
  • Mayo Clinic. "Sweating and body odor." Jan. 25, 2014. (May 15, 2014)
  • MUM. "About MUM." (May 14, 2014).
  • Newman, Andrew Adam. "Two sides to a Deodorant Campaign." The New York Times. March 10, 2013. (May 16, 2014)
  • Poucher, W.A. "Poucher’s Perfumes, Cosmetics and Soaps." Blackie Academic & Professional. 1993. (May 16, 2014)
  • Romanowski et al. "Evaluation of polyhexamethylene biguanide (PHMB) as a disinfectant for adenovirus." National Institutes of Health. 2013. (May 16, 2014)
  • U.S. Food and Drug Administration. "Triclosan: What Consumers Should Know." Nov. 25, 2013. (May 15, 2014).
  • Yazdankha et al. "Triclosan and antimicrobial resistance in bacteria: an overview." National Institutes of Health. 2006. (May 16, 2014)


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