The Frenemy Within

Tom Easton

An ecosystem is a combination of living species and the environment in which they live. An ecological community is just the living species. There are a great many communities. There are even communities on and within human beings, consisting of the bacteria and fungi—and even the generally harmless follicle mites[1]–on our skin and the bacteria, fungi, viruses, and various parasites in our guts.

Years ago, when teaching an environmental science course, the topic was communities. I assigned the class to write a paper describing one. One pair of students chose to write on the community inside our guts, but handed in virtually the same paper. A little checking revealed that both were copied verbatim from a website peddling herbal remedies guaranteed to keep you from ever seeing in the toilet bowl a long list of parasites. Interestingly, the listed parasites were not ones familiar to a parasitologist. That is, if you did not use the herbal remedy, you would never see them either. The particular herbal product doesn’t seem to be available anymore, but there are a great many herbal “colon cleansers” for sale. Since, thanks to modern hygiene, parasite infestations are now rare, you don’t need to waste your money.

The students of course flunked the assignment—for two reasons. First, they cheated. Second, they were stupid about it—they could have cross-checked what they found. Third—no, I didn’t flunk them for this, but third anyway—if they had done a bit of research, they would have found an immense amount of very interesting material on intestinal parasites.

The connection with wearing shoes alone would have been worth a paper.

Say what? It’s true—until the early twentieth century, kids in the rural American south commonly went barefoot and infestations of hookworms, pinworms, and other worms were common.[2] Public health workers pushed for wearing shoes (and using toilets or outhouses), and infestations were reduced. So, of course, were the symptoms, which—because the worms consume the food their victims eat–included a decided lack of energy. That lack of energy may have more than a little to do with the stereotype of southerners (of all colors) as “slow,”[3] even though worm infestations are now much less common.

Yet internal parasites aren’t all bad.  Consider the “hygiene hypothesis.”[4] It says that our intestinal parasites, fungi, and bacteria have evolved not only to benefit from us but also to benefit us (after all, they depend on us). The microbes comprise our microbiome or microbiota and interact with the immune and other bodily systems in many ways. Parasites appear to as well, for as populations eliminate parasite burdens they become more subject to allergies, asthma, and autoimmune diseases (even, perhaps, multiple sclerosis). One Japanese researcher reportedly infected himself and his graduate students periodically with tapeworms to study their benefits, and other researchers have been trying to use other worms or their components to fight allergies.[5] You can even find do-it-yourself instructions on the Internet.

Most people find the idea of deliberately infecting themselves with—or even tolerating—parasitic worms just a teeny bit repulsive. But there are drugs that can kill worms. Just think of what you do when you find roundworms or tapeworm segments behind your pet dog or cat—you rush the animal to the vet, where a single pill does the job. In other words, a health-promoting worm treatment can be a short-term sort of thing.

Another implication of the hygiene hypothesis is that we should be less obsessed with cleanliness. Kids that grow up on farms or with pets appear to be less likely to suffer from allergies and asthma.[6] And considering the way pets lick their butts and then lick us, you know they are exposing us to various microbes, or even parasites. Fortunately, these things can actually be good for us.

Little kids also pick up microbes by inhaling floor dust and putting toys in their mouths. Let them. They need the exposure. As my grandparents’ generation used to say, we need to eat a peck of dirt before we die.[7]

Buying dish-washing detergent and hand soap with built-in antibiotics is not a good idea.[8] Some of these antibiotics the FDA has actually banned from soap, but there are others. And they don’t make the soap any more effective, while they may promote antibiotic resistance, both in the kitchen and downstream in sewage treatment plants and waterways. Since resistant bacteria are harder to kill with antibiotics, if you get infected with them, you can be in trouble.

And it has been shown that wooden cutting boards, wiped down after use, are more sanitary than plastic cutting boards put through a dishwasher.[9] One hypothesis is that on wood, bacteria are drawn into pores and killed by lignin.

But, but… Yes, we can get sick when we are exposed to the wrong parasites or bacteria. The tropics are rife with schistosomes[10] and guinea worms,[11] among others. There is even a spiny South American fish that follows currents containing ammonia[12]–so don’t pee in the river. Dogs have been reported to infect with flesh-eating bacteria by licking.[13] Water parks can give you brain-eating amoebas.[14] Food preparers can contaminate food; the textbook case is “Typhoid Mary.”[15] Thousands of tons of food are recalled every year.[16] Medical devices—even implants—can be contaminated, and the consequences can be dire.

The hygiene hypothesis does not say that hygiene is irrelevant. It isn’t. But it does say we can overdo it. The really scary stuff is rare. Bear in mind that the immune system reacts best to germs it has seen before. It benefits from exposure. So go ahead and retrieve the potato chip that fell on the floor—but pass on the fried egg. The five-second rule is a Real Thing—research has shown that the less time a piece of food spends on the floor the fewer bacteria it picks up, and that moist food picks up more.

Everything in a house does not have to be squeaky clean. Maybe not even the people, despite the old saying that “cleanliness is next to godliness.” When I was a kid that meant our one bath a week was on Saturday night, in time for Sunday morning church. The rest of the week wasn’t that close to godliness, and not bathing daily didn’t seem to hurt us. It surely still wouldn’t, but we have been listening to the soap and deodorant makers for a long time now.

So much of what we take as normal has been influenced by someone’s quest for a buck. However, if we only bought what we really needed, the economy would crash.


[1] http://blogs.discovermagazine.com/notrocketscience/2012/08/31/everything-you-never-wanted-to-know-about-the-mites-that-eat-crawl-and-have-sex-on-your-face/#.XF2Ef82neUk

[2] http://www.mshistorynow.mdah.ms.gov/articles/241/hookworm-disease-in-mississippi%3A-the-importance-of-wearing-shoes

[3] https://www.pbs.org/wgbh/nova/article/how-a-worm-gave-the-south-a-bad-name/

[4] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2841828/

[5] https://medicalxpress.com/news/2015-08-scientists-benefits-worms.html

[6] https://blog.neogen.com/farm-animals-help-prevent-asthma-and-allergies-in-kids-study-finds/

[7] http://givemeboldness.blogspot.com/2007/11/peck-of-dirt.html

[8] https://www.rd.com/health/wellness/triclosan-antibacterial-soap-dangerous/

[9] https://www.drweil.com/diet-nutrition/food-safety/best-cutting-board/

[10] https://www.cdc.gov/parasites/schistosomiasis/biology.html

[11] https://www.who.int/dracunculiasis/disease/en/

[12] https://www.planetdeadly.com/animals/candiru-fish-swim-penis

[13] https://medicalxpress.com/news/2018-08-dog-saliva-bacterial-infection-amputations.html

[14] https://www.popsci.com/brain-eating-amoeba-spreading

[15] https://en.wikipedia.org/wiki/Mary_Mallon

[16] https://www.recalls.gov/food.html

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