The "hygiene hypothesis" suggests that a reduction in the exposure to infectious agents due to improved health conditions has contributed to the increased incidence of autoimmune disorders in developed countries. In keeping with the hygiene hypothesis, many autoimmune disorders such as multiple sclerosis (MS) are more frequently observed in developed countries. To identify the relevance of hygiene hypothesis in neuro-Behcet's disease (NBD), another chronic inflammatory disease of the central nervous system, we developed and administered a multiple choice questionnaire to evaluate the hygiene conditions and practices of age and gender-matched NBD patients (n = 50) and control MS (n = 50) and headache (n = 50) patients. Overall, MS patients had the highest socio-economic and hygiene features, whereas NBD patients displayed a lower socio-economic status group and showed poorer hygiene conditions than MS and headache controls. These poor hygiene conditions might be increasing the susceptibility of exposure to infectious agents that might, at least in part, trigger the inflammatory responses involved in NBD pathogenesis. (c) 2011 Elsevier GmbH. All rights reserved.