by the rising numbers of asthma and allergy-addled kids, some researchers are pointing the finger at too-clean home environments and overzealous parenting practices.
Generally referred to as the “Hygiene Hypothesis,” the theory that kids’ immune systems need to interact with harmless bacteria in order to develop properly has been around since the late eighties.
After finding that households with large families recorded fewer instances of atopic disorders (asthma and allergies) epidemiologist David Strachan of the London School of Hygiene and Tropical Medicine concluded that “unhygienic” sibling traffic may be good for a child’s immune system.
The theory posits that when forced to take a defensive position against infection, a child’s immune system receives essential early training on how to process irritants and may be less likely to overreact to allergens like dust, animal dander and pollen later on. Taking his findings further, Dr. Strachan theorized that smaller family sizes and consequently higher standards of cleanliness in the modern household might hinder this necessary training.
As a consequence of the work of Dr. Strachan and others, some now believe that early exposure to innocuous bacteria boosts immune system tolerance and reduces the risk of a child developing allergies.
“Children’s exposures early in life may influence which way their immune system develops, although not necessarily a ‘healthy immune system’. Cleaner environments appear to foster the development of allergies, as opposed to children in ‘dirtier’ environments. A child’s genetic background has an influence on this as well. Homes with pets, or living on farms with close contact to farm animals appears to decrease the development of allergies. It appears that the immune system requires exposure to bacteria in order to develop properly. Exposure to cleaning agents and other strong fumes, or to dust, may cause irritation of the respiratory system, but doesn’t appear to adversely affect the immune system directly,” says Dr. Paul V. Williams, allergist/immunologist at the Northwest Asthma and Allergy Center in Mount Vernon, Washington.
Dr. Williams is quick to point out, however, that kids who suffer from allergies do not have “bad” immune systems.
“It is a common misconception that people with allergies have a ‘weak immune system’ and they need to do something to ‘strengthen’ their immune system. In fact, their immune system is quite healthy, it just responds in a different fashion to common environmental exposures that ordinarily would not induce any response at all in those with a non-allergenic disposition. Children with allergies are not more prone to infections or more severe infections on the basis of an altered immune system.”
Many in the scientific community emphasize that the hygiene hypothesis is only theory. In fact, researchers are engaged in looking at a variety of factors, including diet and environmental pollution, to explain the increased numbers of asthma and allergy cases. Moreover, others see the idea as an oversimplification, claiming that while exposure appears to be a significant factor in building a better working immune system, determining what is an appropriate level of cleanliness is problematic.
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