A Little Dirt Won’t Hurt

We are a nation obsessed with cleanliness. Walk into any doctor’s office, hospital, school, or daycare center, and you’ll be greeted by a gallon-sized bottle of hand sanitizer at the door. Go to the grocery store, you’ll find a container of disinfecting wipes to ensure all the nasty bugs on your cart handle are killed.

While staying germ-free can certainly prevent the spread of disease and infections, there is a downside to our “germophobia.” It may be making our younger generations more susceptible to allergic diseases.

Immune Tolerance

Back in the 1980s, epidemiologist David Strachan proposed the “hygiene hypothesis,” which stated that regular exposure to things we consider “dirty”—bacteria, allergens, parasites, and other infectious agents—in early life may help strengthen the immune system and protect against various allergies later in life. This is another example of what we have discussed several times: adaptive stress for our immune system. Here is how it works.

As the body and immune system are challenged with small assaults, the immune system develops tolerance and we stop responding to inoffensive agents in an exaggerated manner. With our overly clean lifestyles these days, our bodies no longer have a chance to build up tolerance early in life like they did in decades past. As a result, our immune systems have shifted toward overblown responses to nonhazardous things like allergens (such as pollens). As a consequence, we develop full-blown allergies, hay fever, and asthma to these otherwise harmless agents.

In his initial study, Dr. Strachan looked at how family size affected the incidence of allergic diseases. He concluded that allergic diseases could be prevented in children thanks to “unhygienic contact with older siblings,” or “acquired prenatally from a mother infected by contact with her older children.”

He went on to say that along with declining family size (and therefore less exposure to germs from multiple siblings), higher standards of personal cleanliness (such as cleaner homes) have reduced the chances of infection within families, resulting in widespread allergies, hay fever, asthma, and allergic skin diseases (such as eczema) in children.1

Over the next decade, Dr. Strachan’s hygiene hypothesis remained of interest to other scientists and immunologists, who further examined the potential links between over-cleanliness and allergies and other diseases, even including multiple sclerosis and autoimmune conditions. Further research even broadened the scope of causative factors to include better sanitation practices, antibiotic use, vaccinations, birth practices, and even the growing migration from rural (dirty) to suburban/urban (less dirty) locations.

A follow-up study by Dr. Strachan in 2000 implicated yet another factor in the rise in allergic disease—better socioeconomic status. He noted a higher prevalence of hay fever and eczema in affluent families compared to poorer families.2

It makes sense…families with more money are able to live in a cleaner environment, are more able and apt to practice personal hygiene, and have greater access to medicines, antibiotics, and vaccinations compared to families with less money.

Simply put, many researchers believe—and studies have confirmed—that many of the things we do to keep ourselves clean in an effort to stay healthy and disease free, may actually be backfiring.3

What Doesn’t Kill You…

So how does this pertain to you and your life? Well, you’ve likely heard the saying, “What doesn’t kill you makes you stronger.” As I indicated in previous letters, that is true with the right type of exercise and fasting, but it is also true with certain immune challenges early in life. Particular infections, including exposure to germs, bacteria, viruses, and other pathogens as well as allergens early in life build an immune tolerance against those very issues later on. In other words, your immune system doesn’t respond so aggressively if it has already developed tolerance when you were a young child.

While I understand this probably goes against your protective instincts as a mother, father, or grandparent, and I would never propose forgoing vaccinations or avoiding antibiotics if your children are truly sick, I do think that we as a society take cleanliness to the extreme.

As you may know, I grew up on a farm. My very loving parents and aunts and uncles would sit my cousins and me at the end of a row and we would play in (eat) dirt for most of the day. We had so much fun! I urge you to encourage your young children to play outside often, if it is possible.

Alcohol-Based Hand Sanitizers

I believe another thing you can do at this very second to help strengthen your immune system is to ditch the alcohol-based hand sanitizers. Research shows that these really are best used by one subset of people—healthcare providers who come into contact with multiple patients with compromised immune systems.4 For everyone else, they may do more harm than good in the long term.

There are three major issues here. First, they prevent adaptive responses for the immune system, as discussed above. Second, the overuse of antibacterial hand gels can lead to the creation of resistant superbugs that no amount of sanitizer can destroy.

Third, all antibacterials—hand sanitizers, cleaning sprays, soaps, etc.—do not distinguish between harmful, disease-causing and beneficial health-enhancing microbes. These products kill both. As I’ve previously discussed, friendly bacteria, known as probiotics, are our first line of defense against pathogenic microbes. Up to 80% of our immune strength comes courtesy of the beneficial bacteria in and around our guts, in our airways, and on our skin. Without a robust microbial environment in and on our bodies, our disease-fighting powers aren’t as strong and we can’t stave off infections as well.

If your hands are dirty, by all means wash them with warm water and some non-antibacterial liquid soap. But squirting the gels onto your (and your children’s) hands multiple times a day helps to create an over-clean environment that may contribute to all the problems I’ve discussed.

Finally, I know there’s nothing as heart wrenching as seeing or taking care of a sick child. While the most common childhood illnesses—strep throat; colds; RSV; hand, foot, and mouth disease; conjunctivitis—are quite miserable, they do help build stronger immunity for the future. Maybe that’s some positive news to think about next time you’re rocking your feverish child or grandchild to sleep.


  1. Strachan DP. BMJ. 1989 Nov 18;299(6710):1259-60.
  2. Strachan DP. Thorax. 2000 Aug;55 Suppl 1:S2-10.
  3. Bloomfield SF, et al. Clin Exp Allergy. 2006 Apr;36(4):402-25.
  4. Hilburn J, et al. Am J Infect Control. 2003 Apr;31(2):109-16.

About Author

Brian Matthews

Brian Matthews is the President of Gene Smart and the leader of our Gene Smart team. His mission is to provide supplements to help you control your inflammation, your weight, and your life, based on the latest scientific information.

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