Revisiting the hygiene hypothesis for allergy and asthma

Abstract

The hygiene hypothesis, which describes the protective influence of microbial exposures in early life on the development of allergy and asthma, has continued its swell of academic interest, investigation, and evolution. This article is focused on studies published in the past 3 years that have furthered the substance and shape of hygiene theory, primarily as it relates to allergic airways and asthma. Recent investigations have furthered an overarching "microbiome hypothesis" to home features, medical practices, and cleanliness behaviors that are suspects in the hygiene effect. Relatively crude markers of the protective microbial environment have been supplanted by culture-independent microbiome science, distinguishing the characteristics of potentially protective microbiomes from pathologic features. Understanding how the microbiome is shaped and affects healthful versus harmful outcomes in the human host is relatively nascent. Good clues are emerging that give mechanistic substance to the theory and could help guide microbe-based therapeutics to fill the allergy and asthma management gap in prevention and disease modification.

Asociación entre infección viral del tracto respiratorio bajo en los dos primeros años de vida y el desarrollo de sibilancias recurrentes en niños de 3 a 8 años

“…Si bien no se realizó la distinción del agente etiológico viral en el presente estudio, lo más probable es que la mayoría de pacientes con exposición positiva, hayan tenido una infección por VSR. No tenemos datos epidemiológicos exactos en nuestro medio, pero en revisiones extranjeras se estima que, en menores de 2 años el VSR es el agente más frecuente en las infecciones virales del tracto respiratorio (14,16 tempranas en la infancia podrían disminuir la probabilidad de desarrollar SRRR ("Teoría de la higiene y atopia") (19), se sabe que los virus son potentes desencadenantes de exacerbaciones de esta enfermedad en todos los grupos etarios (1,18,20). Se ha demostrado también, que la bronquiolitis por VSR, si es temprana en la infancia y severa, podría incrementar el riesgo de episodios de sibilancias hacia la época escolar (11,12).…”

Bedroom Allergen Exposure Beyond House Dust Mites

“…Increasing numbers of studies have also shown that exposure to pets is not limited to allergens. Cats and dogs can alter the abundance, richness and/or diversity of host and home microbiome, which in turn may influence the development of a child’s immune system and responses to allergens, supporting the “hygiene hypothesis” [66, 68–74]. While interactions between bacterial endotoxin and pet allergens have been most extensively studied [30, 75], research interests have expanded into more diverse microbial taxa [68–72, 73••].…”

Microbiome in Chronic Lung Diseases

“…Evidence to support this revised hygiene hypothesis includes observations of the low incidence of asthma in Amish populations in the US, as in this farming community, childhood contact with farm animals exposes them diverse microbiota 73 . The Prevention of Allergy-Risk Factors for Sensitization in Children Related to Farming and Anthroposophic Lifestyle (PARSIFAL) and Multidisciplinary Study to Identify the Genetic and Environmental Causes of Asthma in the European Community (GABRIELA) study groups describe decreased rates of asthma in children growing up in farms in central Europe, compared to children located in the same region not living on farms.…”

“…The premise that sterile environments may predispose patients to asthma, while early childhood exposures to diverse microbial milieu prevents asthma acquisition, is the basis of the hygiene hypothesis 73 . The finding that greater microbial diversity is inversely related to airway hyper-responsiveness is congruent with the recent revision of the hygiene hypothesis that early life exposure to diverse microbes diminishes the risk of developing asthma 74 .…”