Are your kids too clean? Are you kidding?

Several stories appeared in the media over the past couple of weeks about a new study that purports to show higher rates of hay fever and allergies in households that use antibacterial soap. Most antibacterial soaps contain the antibiotic Triclosan, and the theory of this new study is that when you kill too many bugs (because of overuse of antibiotics like Triclosan in soap), kids’ immune systems don’t get the stimulation they need to mature normally, and as a result “attack” the body in the form of allergies and hayfever.

Several things to say about this. Firstly, as you’ve read here before, you don’t need antibacterial soap for proper hand hygiene – regular soap and water work just fine. Secondly, overuse of antibiotics is indeed a bad idea. Evidence does not yet implicate Triclosan in causing more serious infections or germ resistance the way we see with other antibiotics like the ones we and our kids take by mouth, but why use antibiotics if you don’t need them?

But the real question for today is: Does being clean harm kids? The implications of studies like the one mentioned is that kids today may be “too clean.”  This premise is called the “hygiene hypothesis.” What exactly is the “hygiene hypothesis” and do you need to add it to your holiday worry list?

It is true that over the past decades, there has been an increase in the diagnoses of allergic disorders (e.g. asthma, hayfever), as well as autoimmune diseases (e.g. inflammatory bowel disease and lupus), both of which represent over-exuberant immune system reactions (see Chapter 4 in GERM PROOF YOUR KIDS – The Complete Guide to Protecting (without Overprotecting) Your Family from Infections). Conventional wisdom held for many years that the cause of these increases may be related to environmental pollution and toxins (i.e. the junk in the air is causing more wheezing type diseases, and the junk in our diet is causing more bowel inflammation, for example).

In the late 1990s, after reunification, a German investigator compared the occurrence rates of allergic diseases among East Germans living under impoverished and unhygienic conditions with those of West Germans living in more pristine and generally wealthier environments. Rather than seeing the expected higher allergy and asthma levels in the poor population, she saw the opposite – the “cleaner” Germans had more allergies and asthma. This led to the “hygiene hypothesis” that states the following: a certain critical mass of germs and “dirt” is required for the healthy maturation of the immune system. If we clean too much, and prevent too many infections, kids will develop aberrant immune system responses that result in more allergies and autoimmune diseases. That is, the immune system needs to be “taught” to respond normally to everyday challenges and to its own body; that “learning” requires a certain amount of germs and dirt, without which the immune system goes awry.

What are the scientific data to support this hypothesis? Right now, we have the potential for a classic “epiphenomenon”, the existence of two “truths” that may or may not be related to each other. Truth #1 is there are increasing diagnoses of allergies and autoimmune disorders; truth #2 is that those disorders tend to occur with higher frequency in wealthier socioeconomic environments (like the ones, for example, that use antibacterial soaps!). In Africa, where hygienic conditions are poor, the incidence of allergic and autoimmune disorders is lower than in the West. Is this genetic, or due to the beneficial effects of poor hygiene? Similarly low levels of allergic and autoimmune disorders are diagnosed in SE Asia, but that trend reverses itself when SE Asians immigrate to Western countries – their children have Western rates of allergic and autoimmune disorders; that seems to dispel a purely genetic explanation.

But maybe we are simply better at making the diagnoses of those disorders in the West. What factors other than “cleanliness” are associated with a higher socioeconomic class in the West and could explain the observation? Clearly there are many differences between Western societies and African and Asian societies that extend well beyond simple hygiene parameters. And how plausible is it that, with the extraordinary number of exposures kids get everyday at day care, school, and in the backyard (see Chapter 2 in GERM PROOF YOUR KIDS – The Complete Guide to Protecting (without Overprotecting) Your Family From Infections, there is still a deficit of critical germs and dirt resulting in allergic and autoimmune responses by the immune system?

Although the data are lacking for a true “nexus”, that is a proven connection between the two “truths” noted above, advocates of the “hygiene hypothesis” have asserted that overuse of antibiotics, including those in personal cleaning products like soaps and shampoos, contributes to the excessively clean environments that pose a risk for our kids (although the West Germans with lower rates of allergies and autoimmune disorders in the late 1990s did not have antibiotic-containing soaps yet). Addressing the antibiotic exposure factor, a paper published in March, 2006 assessed 8 previously published studies of kids who had received antibiotics in the first year of life and assessed whether that exposure predisposed them to asthma later in life. A small statistical association was found, when all 8 studies were combined, to suggest there may be a somewhat increased risk of asthma following early in life antibiotics – the authors caution that the quality of the original 8 studies was such that a meaningful conclusion cannot yet be drawn on this subject. A single study published in June, 2007 implicated antibiotics in the first year of life and the absence of a dog in the house during the first year of life as risk factors for asthma!

At this time, I recommend that you continue to have your kids wash their hands (simple soaps are fine; see Chapter 9 in GERM PROOF YOUR KIDS – The Complete Guide to Protecting (without Overprotecting) Your Family from Infections), take antibiotics when needed (but only when needed; see Chapter 5 in GERM PROOF YOUR KIDS – The Complete Guide to Protecting (without Overprotecting) Your Family from Infections), and receive all of their childhood immunizations (more on the concern that vaccines make kids too clean in Chapter 7 in GERM PROOF YOUR KIDS – The Complete Guide to Protecting (without Overprotecting) Your Family from Infections). Maintaining a clean home will reduce the number of infections passed around in your household – infections that keep your kids out of school and you out of work. Those infections can also be dangerous and even life-threatening (e.g. food borne infections). Household disinfection in “hot zones” like the kitchen, bathroom, and laundry room is prudent and effective.  Community sanitation of water will prevent a retreat to the days of epidemics of cholera and cryptosporidiosis; maintaining air quality standards and removing household cigarette smoke exposure have been proven (proven!) to reduce asthma and other respiratory ailments.

We’ll wait and watch together to see if the “hygiene hypothesis” stands the tests of time, careful study, and reproducibility (see Chapter 12 in GERM PROOF YOUR KIDS – The Complete Guide to Protecting (without Overprotecting) Your Family from Infections). In the meantime, and until proven otherwise, clean is still better than dirty.

And, take a good look at your kids when they come home from school today – are you really worried that they are too clean?

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