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Hygiene and Cleanliness Won’t Impair Childhood Immunity, Study Finds

drawing of child playing in the backyard getting muddy

Verywell / Madeline Goodnight

Key Takeaways

  • A new study reports that good hygiene won't hurt your child's chances of building a strong immune system.
  • The “hygiene hypothesis” is an ongoing debate between experts on the role of too much hygiene in kids’ building immunity.
  • Not all experts agree with the outcome of the study.

Nose-picking. Mud tromping. Eating a french fry off the diner floor. These normal but dirty kids’ habits were once thought to be beneficial to kids’ immune systems, the idea being that they are getting exposed to germs in a controlled way that might prevent them from getting sick later. So some parents and grandparents would allow all of these in hopes it was building antibodies. But a recent study says this so-called “hygiene hypothesis” isn’t true.

Researchers at University College London and the London School of Hygiene and Tropical Medicine published a study in The Journal of Allergy and Clinical Immunology concluding kids can’t be “too clean” for their immune systems to function properly. They say in the study that their work is important because it shows “how the development of targeted hygiene enables us to modify hygiene behavior so that it preserves essential microbial exposures while continuing to protect against infection.” This means we can tailor our kids’ hygiene to what scientists know about germs and infections. 

Debunking the “Hygiene Hypothesis”


Christina Madison, PharmD, FCCP, AAHIVP
, is an associate professor of pharmacy practice at Roseman University of Health Sciences, and founder of The Public Health Pharmacist. She explains that getting dirty to build immunity isn’t seen as medically proven.

“Building up a ‘strong’ immune system from exposure is not an excuse not to practice good hygiene or to unnecessarily expose children. Being ‘too clean’ is not something the medical community thinks is an issue.” She says the benefits of good hygiene outweigh any perceived benefit from immunity due to exposure, which can also be dangerous in some situations, such as when people avoid vaccines. 

However, in some cases, she has seen these techniques be somewhat beneficial, giving the example of a parent cleaning off a pacifier with her own saliva rather than washing it in the sink. “That actually had benefits because of the antimicrobial properties and protective antibodies of human saliva versus just soap and water,” she said. 

The New Findings, From Vaccines to the Role of the Natural Environment

To clarify further the complicated immunity-building process, the study emphasizes four main findings that help us better understand.

  • Microorganisms found in a modern home are not necessarily the ones we need for immunity.
  • Vaccines do more than just target one infection—they strengthen our immune systems
  • Microorganisms in the “natural green” environment matter for our health
  • Allergies are increased by exposure to cleaning products, not removing germs

To fully understand the terminology in the findings, it can be helpful to learn more about how the immune system works.

Understanding the Immune System

To fully wrap your head around why you should or shouldn’t tell your 6-year-old to stop eating boogers, we have to understand the immune system a little better. It’s not intimidating, and more like your favorite social media network than a scary science class concept.

Maya Shetreat, MD, former pediatric neurologist, herbalist, and author of “The Dirt Cure” says, “The immune system is a social system and is always learning. It likes to meet and greet many different organisms and compounds. This is the way it becomes educated to know who is friend and who is foe. When the immune system isn't exposed to as many kinds of organisms, it becomes suspicious of benign organisms or even parts of our own bodies. Allergies and autoimmune disease are the result.” 

Maya Shetreat, MD

The immune system is a social system and is always learning. It likes to meet and greet many different organisms and compounds.

— Maya Shetreat, MD

She also explains the term “microbiome,” which is the immune system’s constant communication with inner and outer terrain. “Mitochondria are thought to have evolved from bacteria, and they communicate the same way bacteria communicate...as such, the microbes in and on our body are in constant communication with our mitochondria and cells, and influence everything from neurotransmitter, hormone and cytokine production to whether the cell should live or die (apoptosis).”

Cleaning Better and Smarter


Lead author Graham Rook, MD, emeritus professor of medical microbiology at University College London, explained to Medical Xpress that while cleaning the home is good, we need to target hygiene to hands and commonly used surfaces, which is where infection transmission really happens. 

So, if you want to worry about modifying hygiene practices, you can be less concerned about how much dirt you are allowing your kids to eat or roll around in, and more about the content of your cleaning products and how they impact your childrens’ lungs. Some cleaning products have even been potentially associated with miscarriage or increased risk for congenital anomalies, so pregnant women might need to avoid certain types.

For parents trying to improve the home environment for allergy prevention and protection, Madison recommends focusing on proper ventilation and changing filters often. “You can look on the filter to see the amount of particles and possible allergens that it can filter out of the air,” she says. “These should be utilized based on if people in the home are suffering from allergy symptoms.”

Hold Onto Those Masks

While we are all ready to throw those masks far far away, Madison says we might want to rethink that if we are trying to prevent illness, and as part of an ongoing good hygiene practice. “There have been multiple benefits to mask-wearing in the past year including a drastic decline in influenza rates as well as asthma exacerbations and hospitalizations,” she says. 

So before you decide you are anti-mask forever, consider all of the ways your family hasn’t gotten sick during the pandemic due to masks. As always, she continues to recommend frequent and thorough hand washing.

Not Everyone Agrees We Shouldn’t Get a Little Dirty for Immunity

Shetreat says that there are definite benefits for kids’ health from living a non-sterile life. “The updated hygiene hypothesis doesn't state that kids need to be dirtier per se, but that they need to be exposed to many kinds of organisms,” she explains.

“Follow-up studies have shown that growing up on a traditional farm doesn’t mean you’re exposed to more organisms; it’s just that the organisms are tremendously more diverse. Diversity is the key.”

Maya Shetreat, MD

The updated hygiene hypothesis doesn’t state that kids need to be dirtier per se, but that they need to be exposed to many kinds of organisms

— Maya Shetreat, MD

How Can Parents Expose Their Kids to a High Diversity of Organisms?

Shetreat has spent her career proving the benefits of the natural environment and teaching how:

  • Eat fermented foods and fresh fruit and vegetables from the garden
  • Let kids get outside, climb trees, have picnics, grow a garden, and “keep pets or even chickens.”
  • Use sponges to wash dishes
  • Swap hand sanitizer for simple bar soap
  • Wash kids’ hands after the bathroom or before eating, not all the time
  • Less frequent bathing of preadolescent kids when they aren’t physically dirty


While kids don’t need to eat it, Shetreat wants them to get out in nature, saying “one teaspoon of soil has as many diverse microorganisms as people on the planet—it’s the best probiotic around.”

What This Means for You

The study shows that you aren't damaging your kids if you practice regular hygiene. However, as the experts explained here, you don't need to shelter them from outdoor life experiences which could exposes the to a variety of microorganisms that will boost immunity. So, wash and clean your children when they are dirty, but don't overdo it. Reconsider using harsh chemicals in the home for cleaning, and be sure to change filters in ventilation systems often to improve allergies and asthma.

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  1. Rook GAW, Bloomfield SF. Microbial exposures that establish immunoregulation are compatible with targeted hygiene. J Allergy Clin Immunol. 2021;148(1):33-39. doi:10.1016/j.jaci.2021.05.008

  2. Hesselmar B, Sjoberg F, Saalman R, Aberg N, Adlerberth I, Wold AE. Pacifier cleaning practices and risk of allergy development. Pediatrics. 2013;131(6):e1829-e1837. doi: 10.1542/peds.2012-3345