Before the Johns Hopkins University president gives 1,300 graduating students their congratulatory handshake Thursday, volunteers will give them a cautionary dollop of hand sanitizer.

“What can I say? We’re a health-conscious university,” said Dennis O’Shea, spokesman for Hopkins.

Since the influenza epidemic of 2009, gel disinfectant has been spreading around schools like strep on throats. Yet there’s little scientific evidence that harmful bacteria are passed through a casual squeeze of the hands during commencement. One of the first studies to put the handshake under the microscope comes from Hopkins’s School of Public Health, and it shows little danger from dangerous pathogens.

And other, more general research may make deans, presidents and principals question why they ever bother to wash.

Another Hopkins researcher recently found that the automatic faucets common in public bathrooms are harboring excess bacteria, such as legionella. A study led by an Ohio researcher found refillable soap dispensers so prone to contamination that users’ hands may be more bacteria-laden than before they were washed. And a University of Virginia study last year found that alcohol-based sanitizers aren’t very effective in preventing colds or flu.

Still, the hand-shaking Hopkins researcher is not anti-hygiene. Dr. David Bishai is a professor in the School of Public Health, after all.

Watching graduation after graduation, he said, the scary pathogens stuck to the dean’s hands “was all I could think about.” For his study, more than a dozen deans agreed to be swabbed before and after their 2008 ceremonies — though some had to be disqualified for sneaking sanitizer every 10 or 20 students.

Turns out that palms, unless extra moist from stress, just aren’t good receptors for pathogens.

Bishai insists that hand-washing is still a good idea. There’s still bad stuff out there, such as antibiotic-resistant Staphylococcus aureus, or MRSA. But his study, published in the June issue of Journal of School Nursing, found only one dangerous bacterial pathogen per every 5,209 on someone’s hand.

“I thought I’d get a big grant from Purell to study more graduations,” he said. “But no. The level of bacteria at graduations is probably smaller than you thought it was. So chill out: A graduate’s hand is probably not the dirtiest thing you are going to touch on graduation day.”

O’Shea, the Hopkins spokesman, says that despite the new data from one of the university’s own researchers, the sanitizer will likely stay in place at Thursday’s graduation.

He added, “We are a research university, committed to evidence-based best practices, so we might take another look later on. On the other hand, a little hand sanitizer never hurt anybody.”