by Lisa Keilhofer

Is Dirt Good? Excessive Hygiene and the Immune System.

Dirt is good
Letting children play in the dirt is sensible when speaking of rich living soil, full of nutrients and microbes. (Picture: © Phils Photography –

Dirt is Good. That is the title of a book by Rob Knight and Dr. Jack Gilbert published in summer 2018. Dr. Gilbert is one of the world’s leading microbiome scientists at University of Chicago. The full title „Dirt is Good. The Advantage of Germs on your Child's Developing Immune System” indicates the main goal: Giving some guidelines to expecting and young parents, as to how much dirt is healthy for their kids.

An interview with the gastroenterologist, professor and author Emeran Mayer broadcasted on YouTube in December 2018 outlines the main content of the book and shall be summarized here.

Antibiotics as the main culprit

The discussion starts of nailing the excessive use of antibiotics for pregnant women, babies and infants. Dr. Gilbert differentiates between the possibility and the probability of a disease. Especially American physicians tend to prescribe antibiotics to rule out the sheer possibility of a disease. This makes sense judging from the point that antibiotics do not come with any side effects, as it was long assumed. The latest scientific findings, however, suggest a massive impact of antibiotics on the premature microbiome of a kid. So, we definitely should re-evaluate the use of antibiotics. And as paediatricians tend to judge from the traditional point of view, parents should seek a critical and open conversation. Knowing the probability to which a disease will occur makes it easier to decide whether or not a course of antibiotics can be justified or not in regards to the side effects.

Mayer is also asking for Dr. Gilbert’s opinion concerning the use of probiotics as post-treatment to antibiotics. The probiotics are supposed to restore the good part of the bacteria in the human organism that was previously wiped out by the antibiotics. Gilbert does not approve this approach. Some patients are more susceptible than others and relevant scientific outcomes are not available yet. So, Gilbert does not recommend the use of probiotic after-treatments.

Is dirt good? Sounding out the book’s title

Gilbert admits that the book’s title was chosen a bit provocative by the publishers to draw the reader’s attention to the book. Of course, it is not generally true that all kinds of dirt are good. But, as he insists, there is an unjustified and constantly spreading dirt anxiety in western, urbanized societies. Totally excessive measures of hygiene resulting in a close to sterile environment are the consequence. Parents are advised to act with sound judgement regarding kind and dose of dirt.

Letting children play in the dirt is sensible when speaking of rich living soil, full of nutrients and microbes. Those stimulate the immune system and support the creating of a diverse microbiome. Sadly enough, in times of industrialized farming, the ground is often dead dust – in the best-case scenario. In the less lucky case, the ground might also be polluted with mercury or fertilizer that is more harmful than helpful for a child’s health.

Jack Gilbert
"Our health is instrinsically linked to the environment around us" - Jack Gilbert (Picture:

Animal hair, dust and pollen – the enemies of hyper-sensitive parents

The same sound judgement is advisable for all environmental impacts. To take a child to “fresh air” is a good idea, to begin with, but in areas of serious air pollution it might be difficult to realize. Sharing one’s home with cats and dogs and not cleaning after every dog’s kiss with disinfectants is a good prerequisite to avoid later allergies on animal hair. On the other hand, loading city kids into busses, shipping them to mass livestock husbandry only to let them get into contact with animal hair is neither sensitive nor feasible.

Easier to regulate is the amount of domestic hygiene. Children of Amish farms who grow up without so-called modern means of hygiene have among the best immune systems. If allergic mice are exposed to dust taken from Amish farms a hypersensitization and reduction in allergy can be achieved. So, it is in any case a good idea to avoid having an aseptic clean house and steer clear from over-aggressive cleansers (except maybe, you have a case of Salmonella in the house, then you may fall back on the previously mentioned sound judgement).

What we can and what we cannot influence

Gilbert closes with some over-all advice on a healthy way of living. Generally speaking, exercising on fresh air and a healthy diet support a sound microbiome. Nutrition high in fibres, little to no industrially processed food, a lot of fish, fruits and vegetables (“eat the rainbow”, as Gilbert puts it) is his recommendation. Under what conditions grew the wheat, the wine, the fruit that I am consuming? What pesticides and fertilizers were used? What is the soil quality? Where does the fish come from, is the water polluted with heavy metal or microplastics?

We can consciously decide for or against food on these criteria. Speaking of environmental protection or regulation of pollution we often have the feeling that we cannot influence these things and are very dependent on politics and industry lobby. But Gilbert is referring to the free market economy. It allows all kinds of products to get on the market, but it is in the customer’s hands what remains on the market. If we all opt to consume only sustainable products free of harmful chemicals impacting environment as little as possible from production to packing – then the free market and also politics will answer these demands over the course of time.

And with this positive outlook Gilbert closes his interview. Many initiatives have already started worldwide. If a sufficient number of people shows a real interest in maintaining our planet in a state that is worth living also for future generations, then we will make exactly this happen.

Lisa Keilhofer
Lisa Keilhofer

Lisa Keilhofer studied at the University of Regensburg. She works in internationalization and as a freelance editor.

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