Notes on Parenting

Insights for parenting babies, toddlers, teens, and young adults.

Thursday, June 21, 2012

Childhood Food Allergies: Are We Too Clean for Our Own Good?

Before having a child I hadn’t given a lot of thought to food allergies. I knew that many kids had them, but no one in my immediate family had ever had problems with food allergies. Around the time of my son’s second birthday we discovered that he had sensitivity to peanuts (technically not an allergy but he still has to stay away from them). After discovering this I became much more interested in the topic of how these allergies develop.

If it seem to you like many of your child’s classmates or friends have food allergies, your perception is correct. Recent statistics estimate that about 3 million children in the U.S. have food allergies. The rate of food allergies among very young children is alarming—about 1 in 17 children under age 3 have a food allergy. These statistics include a variety of food allergies but the most common among children are peanuts, shellfish, eggs, milk, tree nuts, soy, and wheat. There have been pretty significant increases in food allergies in recent decades. When you think about this it is puzzling. Children have been eating these foods for centuries; why the sudden increase in allergies?

There are many theories that scientists have tossed around, but I’m going to discuss just a couple of factors that may be at play. The first one is what is often called the “hygiene hypothesis.” When you consider our modern lifestyle in historical perspective, we are cleaner today than we ever have been. In most American households, there is ample access to soap, running water, and a plethora of anti-bacterial hand cleaners, household cleaners, etc. Unlike kids centuries ago, the kids of today do not regularly dig in the dirt (like on a farm), take care of farm animals, or in some cases, even play outside very much. Some scientists have argued that this sanitized environment limits children’s exposure to common bacteria which help build the immune system. Without this exposure, some kids’ immune systems “misfire” and respond to food ingredients (peanuts, eggs, etc.) as a threat and the result is an allergic response.

There is some evidence to support this theory, although the direct causal link to allergies is still uncertain. First, some studies have found a link between levels of antibacterial agents (such as triclosan found in some antibacterial cleaners/lotions) in children’s urine and the level of antibodies responsible for allergies. Researchers believe that exposure to high levels of these antibacterial agents may disrupt the body’s balance of beneficial and harmful bacteria causing the immune system to respond to common food and environmental factors as allergens.

A second, somewhat related piece of research showed higher rates of allergies among urban kids (9.8 %) compared to kids living in rural areas (6.2%). Some believe this further supports the “cleanliness theory” since presumably urban children are exposed to fewer common bacteria that rural children. Another possibility, however, is that greater population density means that urban children are exposed to other environmental factors that could prompt allergies such as smoke, smog, and air pollutants.

Of course, this “hygiene hypothesis” is not the only theory out there to explain the rise in food allergies in recent decades. Like most complex issues, I imagine there are numerous factors at work in how allergies develop. Other scientists have considered factors such as decreased exposure to sunlight, timing of food exposure, cooking techniques, and of course there are always hereditary factors to consider.

It will probably be many years before scientists fully understand the origin of food allergies, especially the recent rise in them among children. It is interesting and daunting to realize how lifestyle changes in our modern society might be affecting children in a large-scale way. Although science may not have all the answers yet, if you are a parent of a child with allergies, it is helpful to know that there are millions of other parents dealing with the same issues.

A couple of helpful resources:

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