Sorry, parents. If you've been neglecting your housecleaning with the hope that exposure to germs and grime will make your children more resilient, that excuse no longer holds water.
A new report by British scientists debunks the myth that we're too clean for our own good. The report, presented at a national conference on infection prevention in Liverpool on Wednesday, re-examines the decades-old "hygiene hypothesis" and challenges the notion that recent increases in asthma and allergies arise from living in overly clean environments.
The reality is not so simple, says co-author Sally Bloomfield, an honorary professor at the London School of Hygiene and Tropical Medicine.
The hygiene hypothesis is not wrong per se, Bloomfield says, but it misses the mark. While exposure to microbes is important for regulating our immune systems, children are not more likely to develop allergies and asthma if they have fewer infections and live in cleaner homes, she says. Rather, the problem is much broader: As we have adopted modern lifestyles, we have lost touch, over the past two centuries, with a range of germs that our bodies and immune systems have evolved with, she says.
Bloomfield and her fellow researchers lend support to an explanation called the "Old Friends" hypothesis, which suggests our lack of exposure to these old microbes, dating back to paleolithic times, may be making us more vulnerable to a host of disorders and diseases, including type 1 diabetes, multiple sclerosis and other chronic inflammatory diseases.
More research must be done to identify what these microbes actually are, Bloomfield says. "Until we really know what our 'old friends' are, we can't replace them."
And since our diets, environments and lifestyles have changed so much over the past 200 years, reconnecting with these microbes would be a serious challenge.
"Even if we stopped being clean and relaxed hygiene, the microbes around us … probably don't contain the ones that we really need," Bloomfield says, noting that lowering our hygiene and cleanliness standards would merely expose us to new, potentially harmful, pathogens.
Hygiene should therefore be promoted, and the notion of "being too clean" abandoned, she says. More important than spotless counters and gleaming floors is to emphasize measures that protect us from illness, like handwashing, proper respiratory hygiene and food safety.