By David Faulkner
We’ve all seen phrases like “anti-bacterial” and “anti-microbial” emblazoned across aisles of imperious bottles of various soaps, and increasingly in other products such as cutting boards, gym bags and socks. But what is the purpose of antimicrobial compounds in these products? And do we truly need antimicrobial compounds to clean ourselves? The answers are nuanced, and depend on the product in question, but to begin with, we will consider a narrower case, for which there is ample evidence: hand soaps. To discuss the necessity of antimicrobials in hand soaps, let us begin by considering the process of hand washing to begin with.
We wash our hands to reduce disease transmission, and study after study has shown that proper hand washing before preparing and eating food can dramatically reduce rates of diarrheal diseases. Additional studies (1,2) have indicated that stringent hand washing regimens are vital in combating disease outbreaks in hospitals. Unfortunately, most of us don’t wash our hands for the recommended twenty seconds of scrubbing. In fact, one study found that health care workers washed their hands for just under nine seconds on average, while non-healthcare workers spent a little over four seconds at the faucet. The problem with this, is that while it may be satisfying to work up a good lather and rinse it off, the friction of rubbing your hands together and the flow of water to carry the bacteria away are the key to removing unwanted dirt and microbes. And the soap, while helpful for dislodging stubborn dirt and biofilms, is probably not as important as the running water when it comes to removing harmful bacteria – assuming that you’re washing properly. Why, then, is antibacterial soap so popular?
Part of the reason why antibacterial soaps are popular is because they’re useful: multiple studies have shown that they can be used effectively to control outbreaks of hospital-born illnesses, and the FDA has determined that the popular antimicrobial agent Triclosan is useful for controlling cavities and gum disease when added to toothpaste. Most people know that bacteria can make us sick, so it’s natural to think that if regular soap is good, then antibacterial soap must be better. Unfortunately, there’s not much evidence that this is the case for most products, in part because the concentration of antimicrobials found in consumer hand soaps is much lower than the concentrations used in hospital hand soaps, and in part because most people don’t wash their hands for long enough for it to matter anyway. But good marketing is good marketing, and consequently, antibacterial agents like Triclosan has been added to soaps and a menagerie of other products on the premise that it will kill the bacteria that cause disease and unpleasant odors – although the latter claim is even more questionable.
Triclosan is an antimicrobial agent, meaning that it kills microorganisms like bacteria and fungi. It’s considered a broad-spectrum antimicrobial because it can kill a wide variety of microbes, rather than only a specific type. This is because one of the ways that it kills microbial cells is by disrupting the membranes that make up the exterior and inner compartments of the cells, causing their contents to leak. There are several other ways that Triclosan kills bacteria, and one of them is similar to the way that other antibiotics kill bacteria – meaning that if bacteria develop resistance to Triclosan, they may become resistant to other antibiotics as well. Resistance develops when a few bacteria survive an exposure to Triclosan, and they do so because they have developed mutations in their genes that protect them from the chemical. These bacteria then proliferate and can pass the Triclosan-resistance genes on to other bacteria, making them immune as well! Antibiotic resistance affects over 2 million people in the United States each year – some lethally so – and those numbers are increasing. One study found that by the year 2050, antibiotic resistance may cost the world economy over $100 trillion USD (4).
Unfortunately, the risk of antibiotic resistance is not the only reason why we need to reconsider the use of Triclosan in consumer products: growing evidence suggests that it may pose a hazard to human and environmental health as well (5, 6, 7). Much of the Triclosan that enters the environment does so via our sinks and drains when we wash our hands or brush our teeth with products that contain the compound. Not all water treatment processes destroy Triclosan, and the compound may be released into the environment with the rest of the treated effluent, whereupon exposure to direct sunlight can cause Triclosan to break down into molecules from a potent class of environmental contaminants: dioxins. Algae and other aquatic microorganisms can absorb the Triclosan that doesn’t break down in the sunlight, causing the compound to accumulate in the fish and other animals that eat them. High doses of Triclosan have been shown to affect the swimming ability of fish and to disrupt the function of their muscles, and a number of studies have indicated that Triclosan may cause endocrine disruption in mammals although the specific mechanism by which it does so is poorly understood (6, 7, 8, 9, 10).
All of this is to say that while antibacterial compounds such as Triclosan do have their uses – and are indeed quite effective when used judiciously – they probably aren’t necessary in hand soaps, and may do more harm than good when overused. So while it may be tempting to battle germs with antibacterial soaps, the best thing to do is to simply take your time at the sink. Maybe sing the “Happy Birthday” song once or twice?
David Faulkner is a PhD Candidate in Molecular Toxicology at The University of California at Berkeley. He has a few degrees from the University of Michigan, including a Master’s of Public Health. David’s research interests include green chemistry and hazard assessment of industrial toxicants. In his free time, he enjoys running, writing, and YouTube Videos.
- Jones, Rhonda D., Hanuman B. Jampani, Jerry L. Newman, and Andrew S. Lee. “Triclosan: a review of effectiveness and safety in health care settings.”American journal of infection control28, no. 2 (2000): 184-196.
- Pittet, Didier. “Compliance with hand disinfection and its impact on hospital-acquired infections.” Journal of Hospital Infection 48 (2001): S40-S46.
- Arias, Cesar A., and Barbara E. Murray. “A new antibiotic and the evolution of resistance.” New England Journal of Medicine 372, no. 12 (2015): 1168-1170.
- Review on Antimicrobial Resistance (London)., and Grande-Bretagne. Antimicrobial resistance: tackling a crisis for the health and wealth of nations. Review on Antimicrobial Resistance, 2014.
- Fang, Jia-Long, Robin L. Stingley, Frederick A. Beland, Wafa Harrouk, Debbie L. Lumpkins, and Paul Howard. “Occurrence, efficacy, metabolism, and toxicity of triclosan.” Journal of Environmental Science and Health, Part C 28, no. 3 (2010): 147-171.
- Yueh, Mei-Fei, and Robert H. Tukey. “Triclosan: a widespread environmental toxicant with many biological effects.” Annual review of pharmacology and toxicology 56 (2016): 251-272.
- Chalew, Talia EA, and Rolf U. Halden. “Environmental exposure of aquatic and terrestrial biota to triclosan and triclocarban1.” JAWRA Journal of the American Water Resources Association 45, no. 1 (2009): 4-13.
- Cherednichenko, Gennady, Rui Zhang, Roger A. Bannister, Valeriy Timofeyev, Ning Li, Erika B. Fritsch, Wei Feng et al. “Triclosan impairs excitation–contraction coupling and Ca2+ dynamics in striated muscle.” Proceedings of the National Academy of Sciences 109, no. 35 (2012): 14158-14163.
- Fritsch, Erika B., Richard E. Connon, Inge Werner, Rebecca E. Davies, Sebastian Beggel, Wei Feng, and Isaac N. Pessah. “Triclosan impairs swimming behavior and alters expression of excitation-contraction coupling proteins in fathead minnow (Pimephales promelas).” Environmental science & technology 47, no. 4 (2013): 2008-2017.
- Stoker, Tammy E., Emily K. Gibson, and Leah M. Zorrilla. “Triclosan exposure modulates estrogen-dependent responses in the female wistar rat.” Toxicological Sciences (2010): kfq180.