The Case Against Antibiotics in Soap: Part 1

Recently, I saw an article about how the FDA wants to remove antibiotics from hand soap1. To most people, this sounds silly. Antibiotics kill bacteria, and bacteria make you sick, so why should we get rid of this? In fact, reviewers from Rutgers read past papers in late 2011 and found that antibacterial soaps (soaps containing antibiotics) significantly reduce the amount of bacteria on a person’s hands2. As it turns out, the world of bacteria is a very active area of science, and we are learning more about how bacteria interact with us and each other every day. Recently, evidence has suggested a few problems with the most common antibacterial soaps. What are some of these problems, and why are they resulting in new FDA regulations?

We Aren’t Sure If They Are Safe

Basically, anything that you get on your hands is going to end up inside your body, either through itching, or eating, or rubbing your nose/eyes, etc. So it makes sense to be sure that anything you put on your hands is safe to put inside your body, and we’re not entirely sure that’s true of the common soap antibiotics. One of the most common is Triclosan, which is a decent antibacterial and antifungal, but may interfere with proper thyroid function (the thyroid is an important organ that helps control metabolism and growth, especially in the brain3). In 2007, a group from the University of Victoria in British Columbia published a paper looking at the effects of Triclosan on bullfrogs. They found that Triclosan exposure lead to problems with proper rear leg growth, that Triclosan could interfere with normal developmental processes, and may affect how the brain responds to thyroid hormone, at least in frogs4. Because of these risks, the FDA is requiring soap manufacturers to prove that their antibiotics are safe to use before they are put into soaps from now on.

Antibiotics May Be Counterproductive

Your skin already has a lot of bacteria on it, but these bacteria are not a problem5. This is because the vast majority of bacteria are not disease-causing. Actually, it’s recently been suggested that they (as a whole) do some good things for you. For example, these bacteria might actively fight off any other bacteria that you pick up from the environment, since they like living on you and don’t want any competition. This means that a fairly ideal situation for your skin is to always have a population of “good” bacteria around, the bacteria that already live there. When you wash with non-antibiotic soap, some bacteria get picked up by the detergents and washed away, which is true of both good bacteria and any bad bacteria you might have on you. This is fine, though, because you have populations of normal skin bacteria that live on you (in places like skin pores) that “hide” from the soap and can re-colonize an area after the threat of getting washed away leaves. This maintains the relative levels of the bacterial population on skin, meaning that there are always the same kinds of bacteria living on you (it may change slowly over time, but there aren’t any abrupt population changes here).

By introducing antibiotics, you could kill these normally “hidden” bacterial pockets, which would mean that your skin could have a harder time replenishing the normal bacteria population. This could lead to opportunistic bacteria moving into that area. If these bacteria are drug- or antibiotic-resistant, they could be really hard to dislodge again, permanently altering the bacterial population on your hands or skin. On top of that, these bacteria could be disease-causing. This means that, instead of keeping you safe, an antibiotic in soap could be making you more susceptible to infection. A good example of this phenomenon in action is Clostridium difficile or C. diff infection. People get this infection because a course of antibiotics has destroyed the normal population of bacteria living in their intestines, allowing the C. diff bacteria to move in and cause a really bad infection.

I want to stress that this does not always happen. When a doctor prescribes antibiotics, you should take them. Take every pill in the bottle, even after you start to feel better, because that’s the only way to be sure that the bacteria is truly cleared from your system. If you don’t finish the antibiotic course, then another problem could occur. What problem is this? Find out in the next post!


1. http://www.cnn.com/2013/12/16/health/fda-antibacterial/
2. Montville, Rebecca, and Donald W. Schaffner. “A meta-analysis of the published literature on the effectiveness of antimicrobial soaps.” Journal of Food Protection® 74.11 (2011): 1875-1882.  
3. Bowen, R. “Physiologic Effects of Thyroid Hormones.” Physiologic Effects of Thyroid Hormones. Colorado State University, 24 July 2010. Web. 25 Feb. 2014. <http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/thyroid/physio.html&gt;.
4. Veldhoen, Nik, et al. “The bactericidal agent triclosan modulates thyroid hormone-associated gene expression and disrupts postembryonic anuran development.” Aquatic toxicology 80.3 (2006): 217-227.
5. Aiello, Allison E., Elaine L. Larson, and Stuart B. Levy. “Consumer antibacterial soaps: effective or just risky?.” Clinical Infectious Diseases 45.Supplement 2 (2007): S137-S147.

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