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Issue 37: The Hygiene Hypothesis--Too Clean for Our Own Good?

The benefits of hand washing are well known. In fact, Julie Gerberding, M.D., M.P.H., director of the Hospital Infections Program at the CDC says, “Hand washing is of paramount public importance. Washing hands is a major public health intervention to prevent disease—it’s cheap, it’s easy, and it works.” 

The Centers for Disease Control and Prevention (CDC) says that regular hand washing reduces the spread of antibiotic-resistant bacteria and can go a long way toward preventing food-related illnesses. The CDC has reported that foodborne diseases may cause 325,000 hospitalizations each year, 76,000 gastrointestinal illnesses, and 5,000 deaths. An FDA review of 81 foodborne illness outbreaks since 1975 found that food worker illness was a factor in almost all. And in 35 outbreaks, hand contact was identified as a specific factor. 

It’s pretty clear that hand-washing is an important part of proper hygiene. Can you, however, overdo it in the area of hygiene and be too clean for your own good? Some think it is a possibility. In fact a new study published in the American Journal of Gastroenterology looked at whether or not the “hygiene hypothesis” might play a role in the development of inflammatory bowel disease (IBD).

Okay…but what is the “hygiene hypothesis?”

Dr. David Strachan, Professor of Epidemiology at St. George’s Hospital Medical School in London, England first proposed his “hygiene hypothesis” in a 1989 British Medical Journal article. Strachan observed that hay fever and eczema, both allergic responses, were less common in children who hailed from large families (as opposed to families with only one child)—especially those who resided in rural areas. He reasoned that children from larger families were possibly exposed to more germs through contact with their siblings.

Dr. Strachan’s hygiene hypothesis seemed to explain some of the emerging information about how the immune system develops and functions, and included concerns about the “too clean” modern lifestyle. The most recent study in the American Journal of Gastroenterology is one of those looking at being too clean. The study indicates that growing up in an over-clean home may put a child at risk for abnormal immune reactions including IBD, but it was not conclusive.

In this study, Dr. Eran Israeli and colleagues examined “hygienic” markers for a child’s upbringing and that child’s risk for IBD. Here are there findings: Of the nearly 400,000 Israeli teenagers included in the study, 768 -- or 0.2 percent—had been diagnosed with IBD. Teens with one sibling were between two and three times more likely to have IBD than teens with five or more siblings. Additionally, they found that teens who lived in an urban setting were 38 percent more likely to suffer from IBD than their rural counterparts.

The researchers reinforce, however, that the findings do not prove that the hygiene hypothesis is at work in IBD. Israeli, however, adds that it may be possible to lower the risk of IBD in higher-than-normal risk individuals by exposing them to harmless microbes to help regulate their immune responses.

Now that’s something to think over the next time you do some heavy-duty housecleaning.


This information is intended for educational and informational purposes only. It should not be used in place of an individual consultation or examination or replace the advice of your health care professional and should not be relied upon to determine diagnosis or course of treatment.

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