Germs on a plane.

They’re far likelier to get under your skin than snakes, screaming babies or smelly seatmates. And they’re most common on tray tables – a surface that is touched frequently during a typical flight, a new study found.

Travelmath.com recently sent swab-carrying microbiologists to five airports and onto four airplanes and then asked them to determine which surfaces were the dirtiest.

The results will make you reach for the hand sanitizer and rethink what you touch when you travel.

Tray tables, which travelers have been known to use as a platform for everything from eating a meal to changing their baby’s diapers, are the germiest surfaces on airplanes, the experiment found. Next on the list: the overhead air vent, the lavatory flush button and the seat belt buckle.

In airports, the microbiologists identified drinking fountain buttons and bathroom stall locks as the dirtiest places.

Hard to believe?

Charles Gerba, a microbiology and environmental sciences professor at the University of Arizona known as “Dr. Germ,” agrees.

He said his research team did similar studies and found much the same thing. “We also found infleunza virus, norovirus and MRSA on the airplane trays,” said Gerba.

Should you worry? Not if you take the right precautions.

John Zautcke, medical director at the Chicago O’Hare medical clinic, which is opening its first seasonal, in-airport flu shot clinic this weekend, said airports and airplanes are not dirtier than homes or other public places.

“Airports and airplanes get cleaned, but there are hundreds of thousands of people moving through those spaces every day,” he said.

And while it is impossible to avoid coming in contact with the germy places on airplanes and in airports, Zautcke says that’s no reason to stop traveling.

To avoid catching a cold or the flu from germs left behind by other travelers, “use common sense,” says Zautcke, “Try not to touch your mouth after touching any of the germy places on planes and in airports. Wash your hands a lot. Bring along hand sanitizer. Use a towel to open the lavatory door and carry a small package of towelettes.”

Zautcke suggests using a hand sanitizer after buckling or unbuckling your seatbelt on the plane and wiping down the tray table before using it.

And what about the strange looks you may get from a seatmate?

“There is no reason to be ashamed or embarrassed,” said Zautcke, “The important thing is to try to avoid germs and stay healthy. In fact, it would be polite to offer your seatmate some sanitizer as well.”

(My story about germs on a plane first appeared on NBC Travel).