Many airports are hectic and crowded. After all, thousands of passengers pass through them on a daily basis. But the dreaded airport security is not only a hassle for many, it can pose a variety of health hazards.

Jason Tetro, microbiologist and author of the bestseller “The Germ Files” explains that although “there have been no scientific examinations of the microbial contamination of airport floors, studies have looked at surfaces in the airport and have found an incredible number of different types of bacteria, viruses, and fungi.”

The human body sheds millions of microbes every hour and the potential for microbial spread in airports is quite high. Tetro says that “as for the types of microbes found, many can cause infections on the skin and also in the respiratory tract.”

The following list was based on studies and research from various sources, some of which include Oxford Academic and the National Library of Medicine.

Staphylococcus aureus

“This bacterium is known to cause skin infections and can readily grow in the warm environment of your socks and shoes,” Tetro says. “Picking this up may lead to rashes, boils, and cysts.”

Human Papillomavirus

“This virus causes warts and can survive quite well on floors,” Tetro adds. “There have been suspected cases of warts being picked up in airport security so this can be a potential problem for those barefoot enthusiasts.”

Fecal coliforms

“As the name implies, these are bacteria normally found in our intestines. But without proper handwashing, they can end up on surfaces including floors,” says the scientist. “While this is not a problem for the skin, if you happen to touch your mouth after touching your feet, you may end up with some gastrointestinal troubles during your flight.”

Pseudomonas aeruginosa

“This bacterium is commonly found in the environment and poses little threat to our skin,” Tetro says. “But if you have any kind of break in the skin, it could cause an infection requiring medical attention.”

Shewanella putrefaciens

“This bacterium is normally found in the environment but has been identified as the cause of wound and eye infections,” Tetro says. “It still is rare but can be found in airports and may pose a risk to anyone with an open wound or [who] happens to touch their eyes after putting on their shoes.”

Read even more reasons why should never go through airport security barefoot.