If You Give a Baby a Bath and Other Microbial Myths

Review of a blog post: “If You Give a Baby a Bath and Other Microbial Myths”

Between home and public health, wellness, and flu season, the public is interested in microbiology and understanding the bugs we interact with daily. However, like most scientific topics relayed to the public, which are often disconnected from primary studies and convoluted in public opinion, some information is misunderstood. The unfortunate anti-vaccine movement is one example. In her blog post, Dr. Ada Hagan, an American Society for Microbiology Journal Fellow in the Department of Microbiology and Immunology at the University of Michigan, joins the conversation about “microbial myths,” (1) helping to clarify some common beliefs that may have gotten lost in translation. The first myth she investigates is that microwaving your sponge sanitizes it. According to the first hit from a Google search for “how to clean a sponge,” microwaving on high for one minute should “zap 99.9% of germs” (2). Just last week I considered microwaving my sponge. Luckily, I decided to replace my sponge, as Dr. Hagan reports this myth is simply a myth. Citing a Nature Scientific Reports article (3), Dr. Hagan argues that microwaving a sponge doesn’t kill all the bacteria in it. “Cleaned” sponges contained the same number of bacteria as non-sanitized sponges, but the bacterial species represented were different between the two, with heartier bacteria in the microwaved sponges.

The next ‘microbial myth’ is the idea that delaying a newborn infant’s first bath helps establish the skin microbiome. The skin of newborn babies takes a few days to mature, which coincides with the establishment of the microbiome. Although neither Dr. Hagan nor I could find much research into the correlation between timing of the first bath and microbiome establishment, any alteration to the bacterial load of the infant’s skin would affect the early microbiome. This myth is “probably true.”

The final myth Dr. Hagan addresses is that all steps of aseptic technique, like autoclaving media or using a Bunsen burner, are essential. Most of these techniques originated from the labs of Pasteur and Koch. Dr. Hagan admits that she hasn’t practiced universal aseptic techniques. This is similar to my experience in my three rotations so far; each lab seems to follow a different set of protocols with seemingly little effect on contamination frequency or experimental outcome. Dr. Hagan reports that she couldn’t find any research addressing specific steps of aseptic technique but emphasizes that historical precedence in microbiology would suggest many steps are essential. Therefore, this myth is “complicated.”

I decided to follow Dr. Hagan’s example and investigate my own ‘microbial myth’: the idea that ‘double dipping’ spreads germs. MythBusters performed this experiment and found that double dipping did not significantly increase the number of bacteria already found in store-bought salsas (4). In contrast, the show Food Unwrapped found that double dipping in sour cream increased the number of bacteria 100 times over 2 hours (5) A study at Clemson University by Trevino et al. (6) found an increase in bacterial numbers in double dipped sterile water at neutral pH, sterile water at pH 4, 5, and 6, and in three different types of dips (salsa, chocolate, and cheese) over non-dipped and non-double dipped samples. I am more inclined to believe the results of the detailed protocols provided by the Clemson study. However, these types of studies cannot measure any viruses spread by double dipping like herpes simplex or norovirus, which may pose more of a health risk. I believe more research needs to be completed before this myth is settled, especially in defining “germ,” but for now I conclude that it’s true.

Engaging the public in communication about valid scientific research is essential and blogs are one effective way to do this. Even in trivial cases like debunking “microbial myths,” effective communication is useful for illustrating the importance science and the scientific method.


1) Ada Hagan. If You Give a Baby a Bath and Other Microbial Myths. 2 August 2018, posting date. https://asm.org/Articles/Microbial_Sciences/if-you-give-a-baby-a-bath-a….

2) How to Clean a Sponge and Kill Bacteria. https://www.goodhousekeeping.com/home/cleaning/a18731/how-to-clean-a-sp….

3) Massimiliano Cardinale, Kaiser D, Lueders T, Schnell S, Egert M. 2017. ​Microbiome analysis and confocal microscopy of used kitchen sponges reveal massive colonization by Acinetobacter, Moraxella, and Chryseobacterium species. Scientific Reports. 7.

4) Does double-dipping really spread germs? http://www.discovery.com/tv-shows/mythbusters/mythbusters-database/doub….

5) Kells McPhillips. Hold the guac (seriously): double-dipping is a grosser party foul than your realized. 19 June 2018, posting date.  https://www.wellandgood.com/good-food/does-double-dipping-spread-germs/.

6) Judith Trevino, Ballieu B, Yost R, Danna S, Harris G, Dejonckheere J, Philips M, Han I, Moore C, Dawson P. 2009. Effect of biting before dipping (double-dipping) chips on the bacterial population of the dipping solution. J. Food. Saf. 29: 37-48.