If you look for synonyms or associations, you find words like grime, dust, soot, smut, muck, mud, filth, sludge, slime, ooze, dross, scum, pollution, waste, smudges, stains, crud, yuck, grunge, and the list goes on. Dirt certainly has negative associations.

When one isn’t being literal? Well, there’s scandal, gossip, revelations, rumor(s), tittle-tattle, slander, libel, calumny, smears, lowdown, dope, poop. Yep, dirt has lots of black marks against it.

And that’s not even counting dirty words, dirty dancing, dirty jokes, dirty looks, dirty minds…

The slang meaning of “eating dirt” means to accept blame, guilt, criticism, or insults without complaint; to humble or abase oneself.

Is There Nothing Good About Dirt?

The obvious answer comes from growing plants: any gardener or farmer swears by good dirt.

Not so obvious: exposure to dirt and microorganisms can help train your immune system to fight off foreign substances and build resilience to illnesses.

What follows is for informational purposes only. For medical advice or diagnosis, consult a professional.

Dirt and bacteria in the environment help your immune system learn how to react to foreign substances. 

Early exposure to microbes helps children develop regulatory T cells, which are white blood cells that control how the immune system responds to foreign invaders.  Mycobacterium vaccae, a type of bacteria found in soil, can reduce inflammation and improve mood by influencing the release of serotonin. 

Overzealous hygiene practices can wash away or kill off friendly bacteria, but exposure to dirt can help repopulate them. 

Some Ways to Get Exposure to Dirt

Playing in mud can be beneficial for a child’s health.

Outside activities like mountain biking, camping, and hiking can help people come into contact with a diverse microbial ecosystem.

Don’t constantly clean an infant’s pacifier. A dirty pacifier can stimulate your child’s immune system. 

Having a furry pet in the home, regardless of how clean the pet is kept, will introduce bacteria and pet dander into the atmosphere.

And Then There is Actually Eating Dirt!

Written accounts of humans eating dirt date back more than 2,000 years. For many people, all over the world, dining on dirt is nothing out of the ordinary. Now an extensive meta-analysis reported in the June, 2011 issue of The Quarterly Review of Biology helps explain why.

Dr. Sera Young and her colleagues analyzed reports from missionaries, plantation doctors, explorers, and anthropologists to put together a database of more than 480 cultural accounts of people eating dirt. According to this research, the most probable explanation for humans eating dirt (geophagy) is that it protects the stomach against toxins, parasites, and pathogens.

“The database shows that geophagy is documented most commonly in women in the early stages of pregnancy and in pre-adolescent children. Both categories of people are especially sensitive to parasites and pathogens, according to Young and her colleagues. In addition, geophagy is most common in tropical climates where foodborne microbes are abundant. Finally, the database shows that people often eat earth during episodes of gastrointestinal stress. It’s unlikely the intestinal problems are caused by the dirt itself because the type of clay people usually eat comes from deep in the ground, where pathogens and parasites are unlikely to contaminate it. Plus, people usually boil the clay before eating it.”

University of Chicago Press Journals. “Eating dirt can be good for the belly, researchers find.” ScienceDaily. ScienceDaily, 4 June 2011

In one 2017 study, 54% of pregnant women in South Africa ate dirt, and three-quarters of them ate more than 3 teaspoons per day.

Although soil is generally low in nutritive value, deficiencies in iron and zinc may play a role in why some people eat dirt. A 2023 study of children from Sri Lanka suggested that pica (eating things that aren’t food) could indicate a zinc deficiency because the average zinc levels in the children with pica were significantly lower than the average zinc levels in the group without pica.

Note: Eating dirt can be dangerous because soil may contain harmful substances like heavy metals, human waste, and parasites.

Medicinal Uses of Dirt

• Iron-rich smectite and illite clays showed natural antibacterial properties. Kaolin has long been used in diarrhea medicines and is also used in ointments as an emollient. In addition, various clays are used in antacids.

• Numerous bacterial genera and species that produce antibiotics in vitro have been isolated from different soils. Actinomycetes, in particular Streptomyces species, have been the primary resource of clinical antibiotics and other therapeutics.

• Immunologists and allergists in Europe are working on the so-called “farm effect.” Children raised on ecologically managed farms in Central Europe have much lower rates of allergy and asthma than urban children or those raised on industrialized farms. Almost everything points to microbes—in manure, in unpasteurized milk, in stable dust, on unwashed food and, yes, in the soil. How soil microbes and other farm microbes protect against allergic diseases is still a matter of debate.

• Work by Integrative Physiology Professor Christopher Lowry at University of Colorado suggests that exposure to microorganisms in dirt may protect us from anxiety, depression, and post-traumatic stress disorder.

Bottom Line: With dirt, you take the bad with the good.