Allergies, allergies, and more allergies. Where do they come from?

I just had a great question this week on an old blog entry of mine and I started to type a short answer, but then got carried away! So, as to reap the benefits of several hours of contemplation, I'm re-posting my answer here, but with some pictures for illustration. First is the question and then my answer.

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Jen said...
I was wondering what you thought might be the cause of the escalation in food allergies reported in the kids in this study? http://www.dailyrx.com/news-article/peanut-allergies-appear-more-prevalent-14145.html

Why do you think it seems that there is such a higher instance of this in recent times?Do you think it is because of better medical tracking giving a more accurate picture or changes in the environment?

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Katherine said...
Jen,
Good question! I'm definitely not an expert, but I have heard several theories about why people have allergies. The most prevalent one is the "hygiene hypothesis" (http://en.wikipedia.org/wiki/Allergy#Hygiene_hypothesis).

At least this person uses a toilet.

In case you're not familiar, this theory suggests that our society has become increasingly too clean and therefore our immune systems do not develop properly as it shapes and changes throughout our lifetime. Somehow fighting off diseases and infections and gaining more experience with unfiltered air and un-washed foods is somewhat essential to our growth according to this theory.

Some scientists behind this theory go so far as to say that our immune system is built off of that of "early man" where it was necessary to have an extremely high-functioning immune system.

"Early Man" hadn't invented wipies much less the wheel.

Some say we still have that same immune system, but it's no longer getting a complete workout (like having a V8 engine with a bazillion horses, but never going above 30 mph). As a result, it's "bored."

I think it's the hat that's the problem.

I'm not sure how these theories fit with the idea that we can also inherit allergies from our parents. Genetically speaking, what our parents' immune system "learns" while they are alive does not pass down to us. If they get a cold before we are born, we won't somehow be magically immune to that same cold after birth (otherwise I'd be like "my parents version 2.0").

Me 2.0. Don't I look dapper?

We can still become infected by the cold our parents once had. We can only inherit their genotype or the blue prints of an immune system. So "hygiene" can't be the only explanation for why there may be more cases of allergies today.

Like you said, better medical tracking could also be an influence on the statistic you found. Doctors might be keeping better track of this information. Also, it's common knowledge in the medical field that once a pharmaceutical company advertises a drug for some medical problem, people will see their doctor and ask about that medical condition at higher rates than during the previous time period before the advertisement.

Disturbing. Click to view a large image.

Knowledge of allergies and medications for allergies have grown exponentially in the last decade (according to my own observation). More and more people might see information in the news media, infomercials, books, etc, and then realize "hey, you know that problem I've been having? It might be allergies." Then they go to their doctor.

Yes, because I always equate fiber with a sexy stomach. I'm going to go now and talk with my doctor about Benefiber [said sarcastically].

In summary, nobody really knows why we have allergies (and as a result, why there are different trends in allergies). I'm sure you were anticipating that answer. :) Allergies have been a pseudo-scientific area of study for quite some time.

My husband and I are planning to have kids in the next few years, and it's a real concern what genes their going to inherit. All I know is that, Lord willing, we're going to encourage our kids to be as active as possible and to be healthy eaters because I know that's what has really helped me.

Thanks for your question Jen!