Are We Too Clean?

NDSU Microbiology
by NDSU Microbiology

Guest Blogger, Ryan Lenz, Undergraduate in Microbiology

When I was a kid, I can remember numerous times falling and scraping a knee, maybe even crying a little, but then continuing to play. I also remember my dad humorously saying “rub a little dirt on it” to fix any type of injury as if dirt was a cure-all. I sometimes wonder if those types of instances growing up have led to my freedom from allergies.

If you believe the Hygiene Hypothesis, then you would agree that the fact that I grew up on a farm has probably somehow protected me from developing allergies later in my life. The Hygiene Hypothesis basically infers that the decrease in infections in more developed countries has led to an increase in autoimmune and allergic diseases. This idea is basically saying that it is possible that we are becoming too clean for our own good. With hand sanitizers at every corner of every wall, I don’t see why this idea couldn’t be somewhat true.

I remember back in Immunology class, my professor was discussing IgE (immunoglobulin E), an antibody produced to fight against parasites and influence allergic reactions. From my understanding, IgE is made to bind to parasitic antigens, and then cells such as basophils, mast cells, and/or eosinophils are signaled to come by and destroy the invader. I won’t get into too many mechanism details, but what basically happens is the cells release compounds like histamine and cytokines that cause an inflammatory response. If this inflammatory response takes place in response to an allergen, such as dust or pollen, it is called hypersensitivity. Type-1 hypersensitivity, for instance, is the cause of many well-known allergies like asthma and allergic skin rashes.

The hygiene hypothesis explains the cause of certain hyperactive immune responses. If we are truly too clean, then our bodies don't come into contact with as many harmless allergens. If the immune system doesn't have access to its traditional targets, then it essentially becomes "bored" and attacks in response to harmless things like pollen grains.

In the United States, we have seen a substantial decrease in infectious diseases since the industrial revolution and even more so in the past few years. However, we’ve also seen a correlative increase in allergies. Since correlation doesn’t prove causation, I tried to dig deeper into some primary data that I could share. In a review article from the Journal of Clinical Experimental Immunology, the scientists describe many different animal models and clinical trials that reinforce the truths behind the Hygiene Hypothesis. One of particular interest to me was a clinical trial for Crohn’s disease treatment.

Crohn’s disease is an inflammatory bowel disease, an irregular immune response, but the cause isn’t exactly known. In a 2005 study described in the review article I mentioned, 29 Crohn’s disease patients were given ova (or eggs) from a swine-derived parasite called Trichuris suis for a period of 6 months. This parasite treatment improved 72% of the patient’s symptoms. This isn’t the only study out there either. With more and more evidence accumulating, it makes me curious about parasitic treatments. It’s not the most appealing idea for medical treatments, but it’s something I think people with hyperactive immunities that lead to inflammatory diseases could consider one day.

In conclusion, going to daycare, playing in the mud, and taking trips to the farm may not be so bad for your child’s health in the long run. I know I experienced all those things growing up, and I think I turned out okay… maybe...but at least I don’t have any allergies. Ultimately, the next time you debate whether a shower is a good idea or not, please do shower, but don’t be afraid to get dirty every now and then too.

This entry is part of the fall MICR 354 scientific writing students' blog series.

Image: James Heilman, MD.