Allergies Parasites and the Hygiene Hypothesis Term Paper

Allergies, Parasites and the Hygiene Hypothesis

The objective of this study is to explain the relationship between allergies emergence due to parasites based on the hygiene hypothesis and the current information stating how valid this hypothesis is. Towards this end, this study will conduct a brief but intensive review of literature in this area of inquiry. The work of Liu and Leung (2006) report that the hygiene hypothesis has a long history. Categories of allergy and asthma are stated to include specific categories as follows: (1) infections; (2) microbial components; (3) gastrointestinal colonization; (4) soil microbiota; and (5) forces that reduce microbial burden. (Liu and Leung, 2006, p.1063) Stated as fundamental to the hypothesis is "that the microbial exposure of interest can potentially cause both healthful and harmful outcomes." (Ibid, 2006, p.1063) Reported is that this dual way of viewing this is in defiance of the "simplistic tendency to view the relationship as either one way or the other." (Ibid, 2006, p.1063) Reported as the multidimensional determinants of health or disease outcomes in regards to microbial exposures include the following differentiations; (1) microbes or their components; (2) disease phenotypes; (3) elements of time; (4) dosage and exposure combinations; (5) contributions of genetics; and (6) exposure routes. (Ibid, 2006, p.1064) Maizels (2005) reports that evidence has been increasing that "helminth infections can protect the host against Th2-mediated allergic pathologies, even though helminthes themselves are strong Th2 inducers." (p.656) Allergies are reported as being traditionally held as "Th2-mediated inflammatory diseases, involving in the case of allergic asthma, eositophil infiltration into the airway epithelium, the release of long-lasting inflammatory mediators, the elaboration of goblet cells and their production of secretory mucitis, and incremental tissue damage and remodeling which causes longer-term compromise of airway function." (Ibid, 2005, p.656) Therapies that were based on a switching of the "allergen-specific response towards a Th-1 phenotype have met with some success in murine models, but less so in humans." (Ibid, 2005, p. 656) Interesting is that the Th-1 response can also result in inflammation of the airway. It is the opinion of Maizels that the human and animal data model indicates that Tseg cells "are activated in helminth infection and that cells of a similar phenotype can actively suppress airway allergic inflammation…" (Ibid, 2005, p. 656) The work of Schaub, Lauener, and Mutius (2006) reports that there has been a great deal of attention paid to the "advancement of one field in allergy research that investigates the potential link between exposures to microbial sources and the development of allergic diseases." (Ibid, 2006, p. 969) One example stated is that "urticaria is an easily recognizable skin condition, but the variety of factors eliciting these appearances range from infectious stimuli to allergic mechanisms to neoplastic illnesses." (Ibid, 2006, p.969) Bach (2002) states that it is a paradox that infectious agents "…can also suppress allergic and autoimmune disorders." (p.911) It is reported as reasonable to assume "that not a single cause but many will underlie the clinical manifestation." (Schaub, Lauener, and Mutius, 2006, p.969) It is held that "the increased exposure to viruses in a child's environment might foster a milder form of wheezing by suppressing the atopic component." (Ibid, 2006, p.969) This idea is given further validity by studies that investigated the effect of "day care and rhinitis exposure early in life which all showed a protection against atopy in the exposed children." (Ibid, 200, p.971) The work of Okada, Kuhn, Felett and Bach (2005) reports on the hygiene hypothesis for autoimmune and allergic diseases stating that according to the hygiene hypothesis "the decreasing incidence of infections in western countries and more recently in developing countries is at the origin of the increasing incidence of both autoimmune and allergic diseases." (p.1) The hygiene hypothesis is based upon epidemiological data, particularly migration studies that show that individuals migrating.....