The hygiene hypothesis was first proposed in 1989, suggesting that the increase in allergic diseases seen in the Western world over the past 50 years is a consequence of increased cleanliness1. Increased cleanliness leads to reduced exposure to infectious agents and allergens during early childhood. Exposure to allergens during the first year of life is thought to favor the T-Helper 1 (TH1) response when encountered again later in life, whereas a T-Helper 2 response ( TH2) is favored if the first meeting occurs after the first year. of life. The TH2 response stimulates B cells to release immunoglobulin E (IgE), which has been attributed to allergy symptoms2. Although this hypothesis has proven to be very controversial and has sparked much debate, it remains unclear whether increased cleanliness is linked to increased sensitivity to allergens. Riedler et al.3 reported results on 812 European children, from agricultural and non-agricultural households. Previous studies had shown that endotoxins were found in higher concentrations on farms than in other homes4. Participants completed a questionnaire detailing their children's allergies and their child's exposure to stables and farm milk during early childhood. Additionally, blood serum samples were collected for analysis. The serum IgE response to certain allergens, including pollens, microbes, and other infectious agents, was measured. They found that children exposed to farm life during their first year of life were less likely to have reported allergies and also less likely to have positive serum IgE results. Among children exposed to the farm, 1% were diagnosed with asthma and 12% with atopy, compared to 11% and 29% among children not exposed to the farm. T...... middle of paper ...... iss. [online]. Available at: http://www.imvs.sa.gov.au/wps/wcm/connect/aa1661c3-a08a-48ee-86da-d66e6ff4d7ca/allergens-interpreting-results.pdf?MOD=AJPERES [Accessed March 5, 2014 ]6) Perzanowski, MS, Ng'ang'a, LW, Carter, MC et al. (2002) Atopy, asthma and Ascaris antibodies in rural and urban children in Kenya. J Pediatr, 140(5):582-5887) Brooks, C., Pearce, N., Douwes, J. (2013) The hygiene hypothesis in allergies and asthma: an update. Curr Opin Allergy Clin Immunol, 13(1): 70-778) Schaub, B., Liu, J., Hoppler, S. Et al. (2009) Maternal farm exposure modulates neonatal immune mechanisms via regulatory T cells. J Allergy Clin Immunol, 123(4): 774-7829) Nembrini, C., Sichelstiel, A., Kisielow, J. et al. (2011) Bacteria-induced protection against allergic inflammation through a multicomponent immunoregulatory mechanism. Thorax, 66(9): 755-763