The Hygiene Hypothesis -- Redefine, Rename, or Just Clean It Up?

Linda Brookes, MSc; Laurence E. Cheng, MD, PhD

Disclosures

April 06, 2015

In This Article

Is Lifelong Exposure Necessary for Protection Against Allergy?

Some critics of the hygiene hypothesis believe that microbial exposure may need to be continued throughout life to prevent allergies.[9] Dr Cheng is not so sure. "Those children [who grew up on farms] may be protected long term. It is quite possible that the early-life exposures set the stage for everything and that at some point the immune system is set," he said. "People who don't have allergies generally don't develop them later in life; on the other hand, children with allergies tend to have them lifelong. Let's face it, those microbial communities in your gut or on your skin or in your nose are pretty hardy, and they are there for a reason; they have outcompeted other bacterial types, and they have established connections among themselves. They are truly little communities and are often very stable. They can be changed, but in general they don't shift too much. A lot of this is genetics too; the microbes that you pick up are probably evidence of your genetic makeup," Dr Cheng added.

For food allergy, he believes that the issue of lifelong exposure to specific foods to maintain the ability to eat a specific food remains an open question. For instance, with peanut allergy, "we cannot say whether the children at risk could stop eating peanuts and retain their ability to eat them, or whether they are just what we would call desensitized and that if they were to stop regular ingestion, they would go right back to having allergies," he said. Indeed, the authors of the LEAP study are in the midst of a follow-up study (LEAP-On) to address this very question.

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