Between a hygiene rock and a hygienic hard place

Abstract

Suboptimal understanding of concepts related to hygiene by the general public, clinicians, and researchers is a persistent problem in health and medicine. Although hygiene is necessary to slow or prevent deadly pandemics of infectious disease such as COVID-19, hygiene can have unwanted effects. In particular, some aspects of hygiene cause a loss of biodiversity from the human body, characterized by the almost complete removal of intestinal worms (helminths) and protists. Research spanning more than half a century documents that this loss of biodiversity results in an increased propensity for autoimmune disease, allergic disorders, probably neuropsychiatric problems, and adverse reactions to infectious agents. The differences in immune function between communities with and communities without helminths have become so pronounced that the reduced lethality of SARS-CoV-2 in low-income countries compared to high-income countries was predicted early in the COVID-19 pandemic. This prediction, based on the maladaptive immune responses observed in many cases of COVID-19 in high-income countries, is now supported by emerging data from low-income countries. Herein, hygiene is subdivided into components involving personal choice versus components instituted by community wide systems such as sewage treatment facilities and water treatment plants. The different effects of personal hygiene and systems hygiene are described, and appropriate measures to alleviate the adverse effects of hygiene without losing the benefits of hygiene are discussed. Finally, text boxes summarizing this information are provided to function as stand-alone, public-domain handouts with the goal of informing the public about hygiene and suggesting solutions for biomedical researchers and policy makers.

Immunologic, genetic, and ecological interplay of factors involved in allergic diseases

“…A primitive form of antiparasitic immunity is also exhibited in other vertebrates such as avian and non-avian reptiles mediated by the IgY antibody ( 4 – 6 ). However, the survival value for IgE responses has been largely masked with the advent of global deworming efforts, improved sanitation, and changes in global environmental conditions ( 16 , 25 , 157 ). Several theories postulating the basis of the continued persistence of the IgE responses, leading into allergic diseases, have been made in relation to the interactions of the immune system with host genetic, micro-ecologic, and macro-ecologic factors ( 18 , 25 ).…”

“…Several studies have demonstrated the immunomodulatory effect of helminth-derived extracts, indicating their possible role in the prevention of allergic diseases ( 14 , 15 ). This phenomenon was first described as the “hygiene hypothesis,” by the epidemiologist, David Strachan ( 16 , 17 ).…”

The Potential Nexus between Helminths and SARS-CoV-2 Infection: A Literature Review

“…These observations proposed that CHIs induced a Th2-prone response in the host, which modulates COVID-19 severity by restricting the hyper-inflammation associated with the viral infection. The prevalence and severity of SARS-CoV-2 infection and associated pneumonia are higher in developed societies where helminth infection is uncommon [ 69 ]. These outcomes suggest a protective role of CHIs against COVID-19 severity.…”

Reevaluating Biota Alteration: Reframing Environmental Influences on Chronic Immune Disorders and Exploring Novel Therapeutic Opportunities

“…• biota alteration, characterized by the loss of symbiotic organisms such as protists and helminths as a result of the use of technologies aimed at preventing food and waterborne disease [ 4 ].…”