Braun-Fahrländer Charlotte
Institute of Social and Preventive Medicine, University of Basel, Switzerland.
Curr Opin Allergy Clin Immunol. 2003 Oct;3(5):325-9. doi: 10.1097/00130832-200310000-00001.
The hygiene hypothesis proposes an association between the change in exposure to microbes and the increased incidence of atopic diseases in recent decades. Exposure to microbes and childhood infections and their association with atopy has thus attracted much scientific interest. This review focuses on new developments in the field of epidemiology.
Studies in adults confirm that exposure to orofaecal pathogens are associated with less asthma and allergies. In seropositive individuals, no increase in allergy prevalence over time was noted. Similarly, the generational increase in atopy and allergic rhinitis was not observed in individuals who were exposed to a farming environment in childhood. More than 20 studies have been published examining the effect of exposure to a farm environment in children and adults. Most consistently, the 'protective' farm effect was related to livestock farming and thus to microbial exposure. A dose-dependent inverse relationship between exposure to endotoxin in the mattress dust of children and the occurrence of atopic diseases was shown in rural environments in Europe. In addition, the blood cells of farmers' children were shown to express higher amounts of innate immunity receptors. Only a few farm studies have so far included an objective measure of the microbial environment. The examined exposure to endotoxin might partly be a surrogate measure of a much broader spectrum of immunomodulatory microbial compounds present in a rural environment.
The 'hygiene hypothesis' has gained much credibility, but the results should be balanced against the benefits of established hygiene standards.
卫生假说提出近几十年来微生物接触变化与特应性疾病发病率增加之间存在关联。因此，微生物接触、儿童期感染及其与特应性的关联引起了众多科学关注。本综述聚焦于流行病学领域的新进展。
针对成年人的研究证实，接触口粪病原体与哮喘和过敏发生率较低相关。在血清反应阳性个体中，未观察到过敏患病率随时间增加。同样，在童年时期接触农业环境的个体中，未观察到特应性和变应性鼻炎的代际增加。已有20多项研究发表，探讨儿童和成年人接触农业环境的影响。最一致的是，“保护性”农业效应与畜牧业相关，因此与微生物接触有关。在欧洲农村环境中，儿童床垫灰尘中的内毒素接触与特应性疾病的发生呈剂量依赖性负相关。此外，农民子女的血细胞显示出表达更高水平的固有免疫受体。到目前为止，只有少数农业研究纳入了对微生物环境的客观测量。所检测的内毒素接触可能部分是农村环境中存在的更广泛的免疫调节微生物化合物的替代指标。
“卫生假说”已获得很大可信度，但结果应与既定卫生标准的益处相权衡。
