https://www.health.harvard.edu/blog/the-bacterial-horror-of-the-hot-air-hand-dryer-2018051113823 Harvard Health Publishing Harvard Health Publishing Logo Harvard Health Publishing Search Search [ ] Close Shopping Cart Customer Service Content Licensing About Us Login Open mobile menu Menu Free HealthBeat Signup Shop Subscriptions Special Health Reports Online Courses Pay Subscription Bill Common Conditions Staying Healthy Resources Blog COVID-19 Updates Close menu Close Main Content * Common Conditions * Staying Healthy * Resources * Blog Helpful Links * Customer Service * About Us Login * Content Licensing * Free Healthbeat Signup * Subscriptions * Special Health Reports * Online Courses * Pay Subscription Bill Recent Blog Articles blog image 1 Lead poisoning: What parents should know and do blog image 1 FDA approves new surgical treatment for enlarged prostates blog image 1 Kidneys, eyes, ears, and more: Why do we have a spare? blog image 1 Talking to children about tragedies and scary headlines in the news blog image 1 Produce prescriptions may promote better heart health blog image 1 Rare and often aggressive, Merkel cell cancer is best caught early blog image 1 Slowing down racing thoughts blog image 1 Which skin creams are most effective for eczema? blog image 1 Wondering what your lymph nodes have done for you lately? blog image 1 Considering collagen drinks and supplements? / Harvard Health Blog The bacterial horror of hot-air hand dryers iStock-184688295 May 11, 2018 By John Ross, MD, FIDSA, Contributor; Editorial Advisory Board Member, Harvard Health Publishing Follow me on Twitter @JohnRossMD If you're the kind of person who avoids public bathrooms at all costs, you may feel validated, as well as disturbed, by a new study from researchers at the University of Connecticut and Quinnipiac University. They suspected that hot-air hand dryers in public restrooms might be sucking up bacteria from the air, and dumping them on the newly washed hands of unsuspecting patrons. To test this theory, scientists exposed petri dishes to bathroom air under different conditions and took them back to the microbiology laboratory to look for bacterial growth. Petri dishes exposed to bathroom air for two minutes with the hand dryers off only grew one colony of bacteria, or none at all. However, petri dishes exposed to hot air from a bathroom hand dryer for 30 seconds grew up to 254 colonies of bacteria (though most had from 18 to 60 colonies of bacteria). Were the bacteria multiplying inside the hand dryers, or were they being pulled into the hand dryers from the air inside the bathroom? To answer this question, the researchers attached high-efficiency particulate air (HEPA) filters to the dryers, which would eliminate most of the bacteria from the air passing through the dryer. When they exposed petri dishes to air from the hand dryers again, the quantity of bacteria in the dishes had fallen by 75%. As well, the researchers found minimal amounts of bacteria on the nozzles of the hand dryers. They concluded that most of the bacterial splatter from the hand dryers had come from the washroom air. How did the bacteria get into the air in the first place? Unfortunately, every time a lidless toilet is flushed, it aerosolizes a fine mist of microbes. This fecal cloud may disperse over an area as large as six square meters (65 square feet). Aerosols from flushed toilets may be especially harmful in the hospital setting as a means of spreading Clostridium difficile. Is there any good news from this study? Well, the vast majority of the microbes that were detected do not cause disease in healthy people, with the exception of Staphylococcus aureus. Some of the bathroom bacteria, such as Acinetobacter, only cause infections in people in the hospital, or in those with weak immune systems. The others that were found are relatively harmless. In addition, air from real-world bathrooms may contain fewer bacteria than the bathrooms in the study. The sampled restrooms were located in a university health sciences building, and at least some of the bacteria came from experiments going on in laboratories within the building. So what's a person to do to avoid picking up bacteria in a bathroom? You should still dry your hands, as not drying them after washing them helps bacteria to survive on them. Paper towels are the most hygienic way to dry your hands. For this reason, use of paper towels is already routine in health care settings. You may also wish to avoid jet air dryers, which have also been associated with the spread of germs in bathrooms. And remember that your chances of picking up a serious pathogen in a restroom are small. Direct contact with other people is much more likely as a means of acquiring infection. About the Author photo of John Ross, MD, FIDSA John Ross, MD, FIDSA, Contributor; Editorial Advisory Board Member, Harvard Health Publishing Dr. John Ross is an assistant professor of medicine at Harvard Medical School. He is board certified in internal medicine and infectious diseases, and practices hospital medicine at Brigham and Women's Hospital. He is the author ... See Full Bio View all posts by John Ross, MD, FIDSA Share This Page Share this page to Facebook Share this page to Twitter Share this page via Email Print This Page Click to Print Disclaimer: As a service to our readers, Harvard Health Publishing provides access to our library of archived content. Please note the date of last review or update on all articles. No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician. 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