by Gabriel W. Rangel
figures by Michael Gerhardt
How many times per day do you wash your hands? Do you ever think about the type of soap you use? We all know handwashing with soap is an impactful way to maintain health by decreasing the risk of becoming infected with one germ or another. Therefore, using soap with antibacterial compounds added is a no-brainer, right? Wrong! At least according to the U.S. Food and Drug Administration (FDA). In fact, on September 2, 2016, the FDA banned 19 supposedly antibacterial additives commonly found in over-the-counter soaps. So why has the FDA decided to prohibit these seemingly helpful additives?
How does soap work?
To fully understand the FDA’s ruling, we should first understand a little about how soaps clean and disinfect. A quick chemistry refresher will remind us that there are two general types of molecules: polar (things that can be mixed into water, like sugar) and nonpolar (things that cannot be mixed into water, like oil).
Soap molecules are amphipathic, meaning they have both polar and non-polar properties. This gives soap the ability to dissolve most types of molecules, making it easier to wash them off your hands (Figure 1). In terms of illness-causing germs, which are mostly bacteria and viruses, soap has a two-fold effect: one chemical and one behavioral. Firstly, the amphipathic nature of soap loosens the bacteria and viruses off your hands so they can be washed away more easily. Secondly, you tend to wash your hands for a longer period when using soap, because you try to rinse all of it away. Thus, regular soaps don’t necessarily kill bacteria and viruses as much as they simply help you wash them off your skin.
Antibacterial soaps have all the same properties as regular soap, but with an extra ingredient added that is intended to stop the bacteria remaining on your skin from replicating. The idea is that this additive will further protect the hand-washer from harmful bacteria as compared to regular soap. It is important to mention that these ingredients generally have no effect on viruses, so the focus is to reduce the risk from bacterial germs. The most common antibacterial additive found in consumer hand soaps is a compound called triclosan.
Triclosan: the good, the bad, and the unknown
A Swiss company called Ciba-Geigy was the first to synthesize and patent triclosan in 1964, and, by 1970, it was in use around the world as a surgical scrub in hospitals. Today, it is estimated that 3 of every 4 antibacterial liquid soaps sold to the typical consumer contains triclosan as the active ingredient.
While it is a useful part of many consumer products such as toothpastes, there are some concerns regarding the use of triclosan. Studies done on cells and animals in labs suggest the chemical can impact hormone signaling and other biological processes. There is also evidence that accumulation of triclosan in the environment negatively impacts organisms like algae in aquatic ecosystems. However, it is also important to point out that, to date, triclosan has not been directly linked to negative health effects in humans. On the other hand, some of the other additives recently banned by the FDA, like hexachlorophene, have been directly shown to be harmful to humans, especially with high or repeated exposure. Fortunately, for chemicals like these, the FDA has had limitations in place for years to ensure over-the-counter exposure to consumers is within safe limits.
Lastly, there are concerns that triclosan use may increase the risk of generating drug-resistant bacteria. It is well documented that bacteria normally found on your skin can become resistant to triclosan itself. Specifically, triclosan-resistant bacteria typically have mutations in proteins called enoyl-acyl carrier protein reductases (ENRs), which are important for the biosynthesis of cell membranes and are also targets for other clinically used antibiotic drugs like Isoniazid. Thus, when bacteria populations are continually exposed to triclosan, especially from environmental accumulation, they develop mutations in their ENRs to survive the exposure. The major public health concern is that these ENR mutations can also make these bacteria resistant to other antibiotics prescribed by doctors (Figure 2). If this is the case, limiting the use of triclosan to only products where it is most effective could be very important.
The FDA’s Position
Perhaps the most important role of the FDA is to protect public health. One way it can do so is by ensuring compounds in consumer products are “generally recognized as safe and effective.” While there is little evidence to suggest triclosan and other antibacterial additives are directly unsafe for humans, the actual effectiveness of these additives in household soaps had still not been proven as of a few years ago. With that in mind, the FDA issued a ruling in 2013 that required manufacturers to provide direct evidence that household soaps marketed as antibacterial are better at reducing germs and chances of infection compared to plain soaps. Companies had one year to submit their studies.
To date, there has been no conclusive evidence to suggest household antibacterial soaps are an improvement over non-antibacterial soaps. In fact, one study found it didn’t matter whether a household used plain or antibacterial soap containing triclocarban, a compound that is closely related to triclosan and is a part of the FDA ban: both cut the incidence of childhood pneumonia and diarrhea in half.
This means that if you are washing your hands with antibacterial soap, you are exposing yourself and the environment to increased amounts of these chemicals without any measurable benefit. It is for this reason that the FDA has banned adding triclosan and 18 other common antibacterial agents to household soaps, and manufacturers will have until September 2017 to comply with the ruling.
Nonetheless, there are still consumer uses for triclosan that have been proven extremely beneficial, and these are not banned by the FDA. For instance, toothpaste with triclosan has been shown to significantly reduce plaque formation, cavity formation and gingivitis compared to toothpaste without triclosan. Additionally, there are some antibacterial additives in soaps that are not subject to the FDA’s recent ruling. Many companies have replaced the banned ingredients, like triclosan, with one of these three not banned ingredients, and the FDA has granted these companies another year to demonstrate these additives are safe and effective.
“Handwashing is like a do-it-yourself vaccine,” according to the U.S. Centers for Disease Control. Washing with plain soap and water has been shown to reduce bacterial presence on hands by 82%, and studies upon studies point to the beneficial health impacts of washing with plain soap. Clearly the chemical properties of plain soap and its tendency for increasing handwashing time are enough to dramatically increase the health of consumers without adding antibacterial compounds. So, while the FDA has banned household soaps containing many common antibacterial ingredients, handwashing with plain soap will remain a cornerstone of public health and should continue to be a major part of your daily hygiene.
Gabriel W. Rangel is a Ph.D. candidate in the Biological Sciences in Public Health Program at Harvard University.
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Cover image from the US Department of Agriculture