The practice of infecting yourself with parasites to treat allergies and asthma has been mentioned in the press a few times over the last couple of years. It seems a bit extreme and, frankly, gross, but it actually makes some sense immunologically.
The immune system has a bunch of different parts and the part that causes allergies is really designed to fight parasites. There aren’t as many parasitic infections in the Western world as there used to be, and some folks have hypothesized that this might be playing a role in the increased prevalence of allergies.
I’ve tried to explain this in past blog posts by using a dog analogy. Let’s say you own a Labrador Retriever. Labs love to be with people and chase balls and sticks all day long. If, however, you don’t give a Lab some mental and physical stimulation, it will find another outlet, like chewing up your couch cushions or digging up your lawn. In the same way, since the parasite arm of the immune system doesn’t have much to do anymore, it finds another outlet and causes allergies, or so the hypothesis goes.
Based on this hypothesis, people actually started exercising the proverbial dog and infecting themselves with intestinal parasites to treat allergies and asthma with anecdotal reports of success. Remember, dear reader, that the plural of anecdote is not data and to tell whether a therapy really works, you need randomized, blinded, prospective trials. And we have two.
I suppose that using parasites in a study is not really much more risky to the study participant than taking a study drug or using an unproven medical device, but, personally, I would have a hard time signing up for infecting myself with hookworm or drinking a solution containing 2500 pig whipworm eggs. Apparently there are 130 brave souls out there who do not share my apprehension.
In these two studies, participants were either infected cutaneously with hookworm or drank a solution containing 2500 pig whipworm eggs weekly for 3 weeks. (Pig whipworms are not infectious to humans, but do induce immunologic changes in the gut and are a promising therapy for Crohn’s disease.) For their troubles, study participants got an obvious increase in GI symptoms such as pain and diarrhea, but allergy symptom scores didn’t change appreciably. The worm groups did utilize 8 fewer antihistamine tablets during a 60-day allergy season, however.
These were two small studies and, while pig whipworms have shown promise for inflammatory bowel diseases, they might not induce enough systemic changes to affect allergies. These studies also do not address asthma. So while the results weren’t overwhelming, there are still some unanswered questions that will likely result in future studies. Any takers?