Travel is exciting and adventurous, but let's be honest — it can also be exhausting. Even worse is when you catch a cold after a long flight and have to battle a snotty nose in addition to that backlog of emails. You might think the guy with the wicked cough three seats down is to blame, or just sharing air with a couple hundred other humans for hours, but the real reason you get sick may surprise you.

According to the International Air Transport Association, the HEPA filters in the plane's ventilation system can get rid of 99.9 percent of germs and microbes in the air. Plus, only half of the air pumped through the vents is recycled from the cabin; the rest is fresh air from outside.

So if it's not the air, what is giving us all the sniffles?

New research from microbiologists hired by Travelmath reveals your seatback tray is probably to blame. It beat out the bathroom, seatbelt buckles, and the overhead buttons for most unsanitary surface on a plane. (Ew.)

The researchers looked at four flights from different airports, tracking the number of colony-forming units (aka germs and microbes) they found in every sample. With more than 2,155 CFU per square inch, the tray table is far and away the dirtiest surface. The bathroom flush button — which I think we would all assume is the nastiest — collected just 265 CFU, while overhead air vents contained 285 units and seatbelt buckles hosted 230.

Perhaps even more shocking, as TIME points out, is that healthcare professionals advise against flyers directly touching anything in an airplane's bathroom with their hands — and it's not even the most contaminated place on your flight.

But the ick factor doesn't end there: Drexel Medicine declared the seat pocket (and the in-flight magazine) as another breeding ground for bacteria. While it may look like a handy place to store snacks, drinks, and other belongings, passengers like to use seat pockets more like a trash bin than a storage device," the organization warns on its site. "From used tissues to fingernail clippings and dirty diapers, people stuff all kinds of germ-infested materials into airplane seat pockets."

The next time you fly, pack extra anti-bacterial wipes so you can safely dig into those pretzels.