I'll Take a Parasite Please: Helminthic Therapy and the Hygiene Hypothesis

I've been wanting to post on this topic for a while, but never got around to it. I just saw this article in ABCNews titled "Allergy Desperation: I'll Take a Parasite, Please" (linked to from this blog post). It includes a story of a guy named Jasper Lawrence who in desperation from long-term allergy problems decided to infect himself with hookworms. The result was that his symptoms were dramatically diminished (if not cured). Why?

Here's a good excerpt from the article that sums it up:

The hypothesis goes that until recently, humans were fighting off some sort of parasite or another for millions of years, ever since humans evolved into humans. That co-existence eventually led humans to evolving an immune system that worked with parasites.

"When you're born you have an immune system, but your immune system is a blank slate," said Weinstock.

Weinstock explained that just as humans create a functioning digestive system by populating their digestive system with bacteria, humans historically developed an immune designed to account for parasites in the body.

But in the last 150 years, the industrialized world's clean food supply and plumbing suddenly removed parasites from people's bodies. In response, researchers now widely think that people's immune systems stopped developing properly.

Weinstock said most people still have a powerful "attack" function of their immune system, but that many believe the immune system does not develop to regulate properly in the absence of helminthes (parasitic worms).

"People who are not exposed to helminthes have sloppy regulation," said Weinstock. As a result some people's immune systems go off kilter and misfire against their own bodies creating autoimmune disorders such as allergies, asthma, or inflammatory bowel disease.

There has been a lot of research into this area and the general "hypothesis" mentioned has been around since the 1980's. The theory is called the hygiene hypothesis. Basically, our overly hygienic lifestyles in developed nations (particularly in the northeast) means that our immune systems have not been properly balanced and exposed to regulating agents. The lack of this exposure causes all sorts of downstream effects when your body encounters mostly innocuous allergens -- basically it over-reacts. The type of therapy described in the article, helminthic therapy, is meant to correct this problem (albeit later in life than probably should have been the case).

In helminthic therapy, you purposely expose the body to parasites such as hookworms. This exposure forces the immune system to develop the proper regulation systems and as a result it no longer over-reacts.

Sounds great! Pass the bowl of hookworms over so I can load up. Perhaps not so fast. Immune development is really complex and many of these parasites can have serious side effects (... they are parasites after all ...), so it's likely wise to wait for many of the clinical trials underway to be completed. You never know, within a few years you may find hookworms in the same category as probiotics!