Arielle C. found this article about the dangers of handwashing:
The journal of Applied and Environmental Microbiology published an article that talked about contaminated soap dispensers causing an increased amount of microbes able to cause disease. Carrie Zapka is the lead researcher on this study, but also had a team of scientists from BioScience Laboratories in Bozeman, Montana and the University of Arizona, Tucson. Zapka and her team evaluated bulk-soap-refillable dispensers in community settings. She believed liquid soap could become contaminated with bacteria.
In order to test this, they went to an elementary school, where they found 14 of the soap dispensers were already contaminated. They had the students and staff wash their hands with the “infected” soap. They measured the bacteria levels before and after they all washed their hands, only to find out that the bacteria level increased by 26-fold. The scientists found Gram-negative bacteria on their hands. This proved that washing hands is only effective when using uncontaminated soap. At the end of this study the school replaced the bulk-soap-refillable dispensers with sealed-soap dispensers. A year went by and none of the dispensers were found to be contaminated.