Allergies and Me 07: Considering Allergies Through the Lens of Parasitic Infections

 Allergic reactions are ranked by severity, starting with anaphylaxis, followed by oral allergy syndrome, and then asthma and allergic rhinitis. Anaphylaxis is thought to serve a purpose: preventing the total extinction of a genetically related population. Furthermore, regarding the wheat allergy caused by "Cha no Shizuku" soap—a form of oral allergy syndrome—it is suggested that the problem lay in the wheat protein entering the body through the skin, rather than being an error in the immune response itself. This raises the question: might some symptoms of asthma and allergic rhinitis actually be correct, appropriate responses?

 Writing this might lead some to mistakenly believe I think allergies require no treatment simply because they are normal reactions; however, that is certainly not the case. I believe that understanding the mechanisms behind allergies paves the way for more effective treatment.

 Let us consider the functions of the immune system and how they relate to allergies, proceeding from the premise that the human immune system is capable of rationally suppressing parasitic infections.

 Textbooks of parasitology describe the characteristics of parasitic infections. Among these, the features I consider to be associated with allergies are: (1) parasites are transmitted through food, water, and soil; (2) parasitic infections are long-lasting; even in the shortest cases, they persist for several years, and in some instances, they can last a lifetime; and (3) even if infected with parasites, a person remains largely healthy if the parasite load is low.

 Regarding point ①, as I discussed in Blog 05, it is logical for the offspring of mammals to possess immunity against the same parasites as their parents; this suggests that allergies are transmitted to offspring through mechanisms other than genetics.Point ② is thought to be related to the difficulty of curing allergies. While allergies are notoriously hard to treat even over long periods, parasitic infections—unlike viral or bacterial infections—persist for a long time, necessitating the long-term maintenance of immunity. I believe the reason why symptoms and test results often remain unchanged despite long-term allergen avoidance (a state that, from the perspective of the immune system, mimics the absence of parasitic infection) is that the immune system has adapted to the chronic nature of parasitic infections. Maintaining allergen avoidance over a long period is difficult, but it is necessary to cure the allergy.

 As for point ③, I'll cover it in the next blog post.