Asthma and allergy are widespread and increasing in prevalence in children.1,2 The hygiene hypothesis suggests that the modern version of cleanliness may be largely to blame, and research suggests two elements that might mediate this effect: endotoxins and genes related to innate immunity.
One study examined the prevalence of asthma and allergy in two communities: the Amish and the Hutterite.3 These two communities have genetic and environmental overlap, as well as similar lifestyle factors—with one major difference: the Amish still farm in small, family farms while Hutterites have larger, more industrialized communal farms. The study found that the Amish children displayed significantly lower allergic sensitization and asthma than the Hutterite children.3
When the researchers examined the dust from each environment, they found it contained strikingly different levels of endotoxins. Mice exposed to the dust from Hutterite homes went on to develop asthma or allergy symptoms, while those exposed to dust from Amish homes did not. They also found that genes that modulate the innate inflammatory response and genes that depend upon nuclear factor kappa-light-chain-enhancer of activated B cells were expressed differently in the Amish versus the Hutterite children.3
Overall, endotoxin levels in the air do not change drastically when comparing farming and urban environments, but endotoxins in dust are much higher around dairy farms.4 Even in urban environments, children exposed to higher levels of endotoxins at school also have worsened asthma symptoms.5 However, for children who do not yet have allergic reactions or asthma, increased endotoxin exposure may be protective, reducing the likelihood of developing either condition.6-7
Learn more about immune dysfunction and inflammation, as well as the antecedents and triggers for immune conditions, at IFM’s Immune Advanced Practice Module (APM). Expert clinicians will present on the latest research and clinical tools for diagnosing and treating patients with immune dysfunction.
- Dogruel D, Bingöl G, Altintas DU, Seydaoglu G, Erkan A, Yilmaz M. The trend of change of allergic diseases over the years: three repeated surveys from 1994 to 2014. Int Arch Allergy Immunol. 2017;173(3):178-182. doi:10.1159/000477726.
- Brozek G, Lawson J, Szumilas D, Zejda J. Increasing prevalence of asthma, respiratory symptoms, and allergic diseases: four repeated surveys from 1993-2014. Respir Med. 2015;109(8):982-990. doi:10.1016/j.rmed.2015.05.010.
- Stein MM, Hrusch CL, Gozdz J, et al. Innate immunity and asthma risk in Amish and Hutterite farm children. N Engl J Med. 2016;375(5):411-421. doi:10.1056/NEJMoa1508749.
- Barnig C, Reboux G, Roussel S, et al. Indoor dust and air concentrations of endotoxin in urban and rural environments. Lett Appl Microbiol. 2013;56(3):161-167. doi:10.1111/lam.12024.
- Lai PS, Sheehan WJ, Gaffin JM, et al. School endotoxin exposure and asthma morbidity in inner-city children. Chest. 2015;148(5):1251-1258. doi:10.1378/chest.15-0098.
- Gehring U, Bischof W, Fahlbusch B, Wichmann HE, Heinrich J. House dust endotoxin and allergic sensitization in children. Am J Respir Crit Care Med. 2002;166(7):939-944. doi:10.1164/rccm.200203-256OC.
- Gehring U, Strikwold M, Schram-Bijkerk D, et al. Asthma and allergic symptoms in relation to house dust endotoxin: phase two of the International Study on Asthma and Allergies in Childhood (ISAAC II). Clin Exp Allergy. 2008;38(12):1911-1920. doi:10.1111/j.1365-2222.2008.03087.x.