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How clean is too clean?

August 15, 2018 Wellness Articles By Sunil Thomas, PhD

In recent years, researchers have uncovered a startling fact: People who grew up in ultra-clean environments were more likely to develop allergies, asthma and autoimmune disorders. In fact, the incidence of these disorders has increased in children over the past few decades.

Scientists call this the hygiene hypothesis. Lack of exposure to microorganisms early in life can mean the immune system is not properly trained or prepared to tackle germs. Over time, the result can be an overactive immune system that is perpetually hyper-ready to pounce on and attack the host.

To more fully explain, let’s take a moment to review a little biology. Our health and wellbeing depend on the nature of the microorganisms we inherit and acquire. For example, microorganisms are responsible for synthesizing vitamins, enzymes and other essential nutrients. A lack of these beneficial microorganisms can lead not only to reductions in these vital nutrients, but also to an increase in non-beneficial—potentially disease-causing—bacteria.

This understanding of the link between microorganisms, overly hygienic practices and disease has come about only in the past few years. Before that, we had the “war on germs” that started in the mid-20th century with the advent of antibiotics and disinfectants. But over the years, misuse of antibiotics and the overuse of disinfectants have led to reduced rates of good microbes and the concomitant impact on immunity.

The immune system is active throughout life—and especially so during infancy and childhood. Babies inherently lick anything, and the microbes they pick up can activate their immune systems. Therefore, an environment that is “too clean” can mean a child will not be exposed to enough microorganisms and thus may end up with an immature immune system. And that, in turn, can lead to allergies and autoimmune disorders later in life. Thus, parents who frequently disinfect toys, furnishings and other objects may unexpectedly do more harm than good for the health of their children.

It’s not just objects in the nursery or playroom that parents need to focus on. Studies show that people who drink bottled water but not tap water are more prone to allergies, as bottled water is more likely to be free of microbes. Studies also have shown that people who eat from plates washed in dishwashers have more allergies than those who eat from dishes that have been washed manually. A dishwasher tends to wash away all bacteria, while manual washing often leaves behind some of the bacteria that may benefit the immune system. (In case you were wondering: Antimicrobial soaps have not been shown to have any benefit over conventional soaps.)

In short, for the vast majority of people, your home does not need to be as sterile as an operating room or hospital. Basic hygiene is good, but too much hygiene can be detrimental for long-term health.

Main Line Health serves patients at hospitals and health centers throughout the western suburbs of Philadelphia. To schedule an appointment with a specialist at Main Line Health, call 1.866.CALL.MLH (225.5654) or use our secure online appointment request form.

Sunil Thomas, PhD is a scientist who specializes in immunology at the Lankenau Institute for Medical Research. He is the editor of three books, two of which are textbooks on vaccines.