Histamine, Hygiene Hypothesis, & Hookworms

If you’re like me and millions of other Americans you’ve spent this spring being an itchy, sneezing, mucous-y mess. In this week’s Worldwide Wednesday I’m talking about allergies– the immune system’s reaction to pollen and otherwise harmless substances (dubbed allergens) and the ruiner of my favorite season.

Scanning electron microscope image of pollen grains from a variety of common plants.

Histamine

We’ve all heard of them before, but what is histamine and what does it do? Histamine is a chemical compound produced by cells of the immune system, such as mast cells, and is the primary culprit that causes the miserable symptoms of allergies. That is because histamines induce capillaries to leak out fluids resulting in sneezing, watery eyes, and a runny nose. Learn how the release of histamines from mast cells is triggered by allergens and how anti-histamine drugs work:

(Note: I liked the videos about allergies and antihistamines on about.com better, but I couldn’t figure out a way to embed them.)

Hygiene Hypothesis Challenged

As I mentioned, allergies are actually an immune response and the main players have other roles in immunity. For instance, the class of antibodies called Immunoglobulin E (IgE), which bind to allergens and triggers the release of histamines, appears to be the main line of defense against parasitic infections. Histamine, on the other hand, is part of the inflammatory response.

So what would cause the immune system to react to otherwise innocuous substances? One widely accepted explanation that takes into account the prevalence of allergies in developed countries is the hygiene hypothesis. Since we have effectively eradicated parasitic infections and live in increasingly cleaner and relatively sterile environments, we have reduced our exposure to infections pathogens and parasites especially during childhood. As a result the body’s immune system, which would normally be pre-occupied dealing with parasitic infections, becomes “bored” and starts mistaking harmless substances for potentially hazardous ones. Recently, however, some scientists have begun to look at allergies not as our immune system going rogue but rather that “runny noses, coughs and itchy rashes keep toxic chemicals out of our bodies, they argue, and persuade us to steer clear of dangerous environments.”

Hookworms 

The concept underlying the hygiene hypothesis has inspired some squirmy solutions. Some people, desperate for allergy relief, have turned to infecting themselves with parasites such as the hookwormNecator americanus. The idea behind this treatment, known as helminthic therapy, is to keep the immune system’s hands tied up dealing with the parasitic infection so that it can’t trigger allergies.

N. americanus. “What’s it going to be, me or allergies?”

While there is some evidence that this therapy works, its efficacy is still being studied. But that isn’t stopping this doctor from experimenting on himself. Neither is it stopping Jasper Lawrence, who deliberately infected himself to combat allergies and asthma. You can catch the story of how he took it one step further and started selling hookworms as a business and how shortly after he had an ominous visit from the FDA.

Related Reading:

While most allergy treatments focus on blocking histamines, Finnish scientists are taking a different approach: vaccination.

Scientists at the University of Eastern Finland led by Professor Juhu Rouvinen, in cooperation with Professors Kristiina Takkinen and Hans Söderlun from VTT, a technical research center in Finland, discovered unique IgE‐binding structures in allergens. They say these structures can be genetically modified so they do not bind IgE anymore, but they can still induce the production of the immunoglobulin G (IgG). IgG protects you from allergic symptoms by actually prohibiting the formation of IgE-allergen complexes and could, in theory, prevent the degranulation and histamine release from white blood cells. The modified allergens are produced using modern molecular biology and biotechnology.

It seems a little vague since I can’t find anything published, but it would appear to be a lot of work since I imagine for the vaccine to prevent all allergies it would require modifying ALL allergens.

Meanwhile, a study from the Fred Hutchinson Cancer Center links allergies to higher blood cancer risk. But as the report concedes, “the added risk is so small that no new screening guidelines are currently planned.” Which made me wonder why this was even reported on the first place. As with the vaccination report, I couldn’t find anything published to read and evaluate.

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One response to “Histamine, Hygiene Hypothesis, & Hookworms

  1. Pingback: Autism in the News « Amasian Science·

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