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.
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.
- Antiperspirants Info. "Antiperspirants & Deodorants." (May 15, 2014) http://www.antiperspirantsinfo.com/en/antiperspirants-and-deodorants/about-antiperspirants-and-deodorants.aspx
- Goodman, Brian. "Deodorant Scientists Arm Against Odor." CBSNews.com. June 22, 2006. (May 15, 2014) http://www.cbsnews.com/news/deodorant-scientists-arm-against-odor/
- Lewis, Kristin. "The History of Stink." Scope. Nov. 12, 2012. (May 15, 2014) http://www.scholastic.com/scopemagazine/PDFs/SCOPE-111212-PairedTexts.pdf
- Mayo Clinic. "Sweating and body odor." Jan. 25, 2014. (May 15, 2014) http://www.mayoclinic.org/diseases-conditions/sweating-and-body-odor/basics/causes/con-20014438
- MUM. "About MUM." (May 14, 2014). http://www.mum-deo.com/about-mum/history/
- Newman, Andrew Adam. "Two sides to a Deodorant Campaign." The New York Times. March 10, 2013. (May 16, 2014) http://www.nytimes.com/2013/03/11/business/media/degree-deodorant-introduces-unisex-ad-campaign.html?_r=1&
- Poucher, W.A. "Poucher's Perfumes, Cosmetics and Soaps." Blackie Academic & Professional. 1993. (May 16, 2014) http://www.monzir-pal.net/Industrial/Deodrants.pdf
- Romanowski et al. "Evaluation of polyhexamethylene biguanide (PHMB) as a disinfectant for adenovirus." National Institutes of Health. 2013. (May 16, 2014) http://www.ncbi.nlm.nih.gov/pubmed/23450376
- U.S. Food and Drug Administration. "Triclosan: What Consumers Should Know." Nov. 25, 2013. (May 15, 2014).http://www.fda.gov/forconsumers/consumerupdates/ucm205999.htm
- Yazdankha et al. "Triclosan and antimicrobial resistance in bacteria: an overview." National Institutes of Health. 2006. (May 16, 2014) http://www.ncbi.nlm.nih.gov/pubmed/16922622