Written by Joyce Smith, BS. American adults with allergies, especially but not exclusively to nuts and seasonal pollen, have lower richness and altered composition of their gut microbiota.

allergiesAllergies represent one of the country’s most common, yet often overlooked diseases. Included are type 1 hypersensitivity disorders 1, and asthma 2, both of which are clinically important and increasingly prevalent, particularly in the US population. Functional and observational studies suggest that a higher standard of modern hygiene that reduces or limits early life exposure to bacteria, is contributing to our seasonal pollen allergy or eczema 3. The prevailing epidemiology of allergic disease suggests the “hygiene hypothesis” as a “socioeconomic gradient” with hay fever and eczema more prevalent in affluent families. Recent studies have found that farm children compared to other children in rural areas have less allergic rhinitis, asthma and atopic dermatitis, which researchers attribute to environmental proteins such as house dust mites, grass pollen and food allergies 4. Interestingly, based on serological or skin prick testing, households with at least 2 dogs or cats are 70% less likely to react to common respiratory antigens 5.

In a previous analysis of publicly available data from the American Gut Project (the world’s largest open-source science project, Goedert et al 2014 6, attempting to understand the microbial diversity of the human gut) found a distinct difference in the composition of the fecal microbiota of adult volunteers who were born by cesarean section. To better understand a potential association between infant and adult allergies and gut dysbiosis (alterations in the gut microbiota, 7 Hua et al in 2016 did a comprehensive analysis using questionnaires and publicly available data from 1,879 American Gut Project participants (mean age, 45.5 years; 46.9% male). Microbiome and phenotypic data; richness (number of observed species), alpha diversity and individual taxa tests, composition (beta diversity) test, and specific taxa associated with multiple allergy traits were compared from adults with allergy versus those adults without allergy to foods (peanuts, tree nuts, shellfish, other) and non-foods (drug, bee sting, dander, asthma, seasonal, eczema). Self-reported allergy prevalence among the participants was 82%. Three % of participants reported allergy to peanuts, tree nuts, or shellfish and 9% reported allergy to other foods. Non-food allergies ranked with 4.7% for bee sting up to 40.5% for seasonal.

Specifically, fecal microbiota richness and composition was significantly lower with total allergies (p=10-9) and five particular allergies (P≤10-4). Richness odds ratios were 1.7 (CI 1.3–2.2) with seasonal, 1.8 (CI 1.3–2.5) with drug, and 7.8 (CI 2.3–26.5) with peanut allergy. Allergic participants also had significantly altered microbial community composition (unweighted UniFrac, P = 10−4 to 10−7) that was evident with all allergies except asthma, bee sting, and eczema. The dysbiosis was most marked with allergy to nuts and seasonal pollen and was driven by a higher abundance of Bacteroidales and a reduced abundance of Clostridiales taxa. Women reported more drug allergy while obese participants reported more seasonal allergy. Owning a cat or a dog had no association with either microbiota richness or composition.

This study had a number of weaknesses including the use of self-reported questionnaires and potentially misclassified allergies. Also, the cross-sectional design, which represented only one time point could not distinguish whether the observed dysbiosis preceded or followed the allergy development. While this study of an allergy associated dysbiosis supports the hygiene hypothesis, the origin of the dysbiosis is unknown. Also unknown is whether prevention or improvement of the dysbiosis can modify allergy prevalence or severity. The authors are hopeful that future clinical trials and other longitudinal studies will address the question of whether prevention or improvement of the dysbiosis can modify allergy prevalence and severity.

Source: Hua, Xing, James J. Goedert, Angela Pu, Guoqin Yu, and Jianxin Shi. “Allergy associations with the adult fecal microbiota: analysis of the American Gut Project.” EBioMedicine 3 (2016): 172-179.

2352-3964/© 2015 The Author. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Click here to read the full text study.

Posted August 7, 2018.

Joyce Smith, BS, is a degreed laboratory technologist. She received her bachelor of arts with a major in Chemistry and a minor in Biology from  the University of Saskatchewan and her internship through the University of Saskatchewan College of Medicine and the Royal University Hospital in Saskatoon, Saskatchewan. She currently resides in Bloomingdale, IL.

References:

  1. Haapasalo M, Shen Y, Qian W, Gao Y. Irrigation in endodontics. Dental Clinics of North America. 2010;54(2):291-312.
  2. Sheikh A, Smeeth L, Hubbard R. There is no evidence of an inverse relationship between TH2-mediated atopy and TH1-mediated autoimmune disorders: lack of support for the hygiene hypothesis. Journal of allergy and clinical immunology. 2003;111(1):131-135.
  3. Strachan DP. Family size, infection and atopy: the first decade of the’hygiene hypothesis’. Thorax. 2000;55(Suppl 1):S2.
  4. Ege MJ, Mayer M, Normand A-C, et al. Exposure to environmental microorganisms and childhood asthma. New England Journal of Medicine. 2011;364(8):701-709.
  5. Ownby DR, Johnson CC, Peterson EL. Exposure to dogs and cats in the first year of life and risk of allergic sensitization at 6 to 7 years of age. Jama. 2002;288(8):963-972.
  6. Goedert JJ, Hua X, Yu G, Shi J. Diversity and composition of the adult fecal microbiome associated with history of cesarean birth or appendectomy: analysis of the American Gut Project. EBioMedicine. 2014;1(2-3):167-172.
  7. Hua X, Goedert JJ, Pu A, Yu G, Shi J. Allergy associations with the adult fecal microbiota: analysis of the American Gut Project. EBioMedicine. 2016;3:172-179.