Allergies and Me: 06 Are allergies a case of the immune system running out of control?

 In my previous blog, I discussed the idea that allergies might be transmitted to children through mechanisms other than genetics—specifically, that they might represent one of the functions of Th2 immunity. On the other hand, many people seem to believe that, since allergies represent an immune system gone out of control, it is a mistake to regard the various phenomena associated with it as functions. Here, I will explain my perspective on this matter.

 Sixteen years ago, a wheat allergy caused by a soap called "Cha no Shizuku" occurred in Japan.People who used soap containing hydrolyzed wheat protein developed wheat allergies; the Th2 immune system recognized the wheat protein that had entered through the skin, leading to oral allergy symptoms or anaphylaxis upon the subsequent ingestion of wheat-based foods. Oral allergy symptoms—such as itching and swelling of the lips, tongue, and throat immediately after consuming the offending food—can be interpreted as a warning signal from the Th2 immune system to stop eating; in other words, the Th2 immune system was functioning normally, and the error lay in the fact that wheat components had entered the body through the skin. As for anaphylaxis, the concept of the "selfish gene" suggests that this, too, serves a functional purpose: by causing the death of an individual infected with a lethal pathogen (a "scorched-earth" strategy), the immune response prevents the total annihilation of the population sharing the same genes.

The prevailing view is that allergies are a runaway Th2 immune response; however, regarding the wheat allergy caused by "Cha no Shizuku" soap, I believe the Th2 response did not simply run wild on its own but was actively triggered to do so. What, then, about asthma, allergic rhinitis, and other oral allergies? I consider these, too, to be the result of a Th2 immune response being forced into a state of runaway activity—a topic I hope to discuss at a later time.