From a medical point of view, not all religious practices are always 100% risk free. See, for example, a recent Improbable article : ‘Official word: The body of Christ is not and cannot be gluten-free.’ But gluten intolerance is not the only area for concern – what about Holy Water in hospital chapels for example – is it safe? A 2012 paper published in the German journal Hygiene & Medizin : Infection Control and Healthcare describes a clinical investigation, the results of which suggest ‘perhaps not always’. ‘Holy water of hospital chapels as a possible source for nosocomical [sic] infections’ by Hubert Weiß.
The ongoing discussion about effective preventive measures against nosocomical [sic] infections concentrates very much on activities of hygiene management and on the search for all possible ways of introduction of germs into the clinical area. This analysis investigates whether holy water in hospital chapels may provide a possible reservoir for a contamination of patients in the clinical area as well as hospital equipment. The microbial count and the spectrum of bacteria detected in holy water lead to the conclusion that holy water should be integrated into the monitoring and the hygiene management of hospitals as a critical control point. This paper develops suggestions for the expansion of hygiene management and for the reduction of microbial counts in holy water fonts. Finally, liability issues will be discussed.”
NOTE: It’s very likely that the word ‘nosocomical’ used above should in fact be ‘nosocomial‘ – meaning an infection acquired in hospital (from the Greek word nosokomos ‘a person who tends the sick’.)