Barbeito, MS; Mathews, CT; Taylor, LA (1967). “Microbiological laboratory hazard of bearded men”. Applied microbiology 15 (4): 899–906. PMID 4963447

“An investigation was conducted to evaluate the hypothesis that a bearded man subjects his family and friends to risk of infection if his beard is contaminated by infectious microorganisms while he is working in a microbiological laboratory. Bearded and unbearded men were tested with Serratia marcescens and Bacillus subtilis var. niger.Contact aerosol transmission from a contaminated beard on a mannequin to a suitable host was evaluated with both Newcastle disease virus and Clostridium botulinum toxin, type A. The experiments showed that beards retained microorganisms and toxin despite washing with soap and water. Although washing reduced the amount of virus or toxin,a sufficient amount remained to produce disease upon contact with a suitable host.”

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