What you don’t see can kill you – or at the very least completely gross you out.

A new study by Travelmath has exposed just how dirty hotel rooms in the United States can be. It sent an investigative team to nine different hotels to gather 36 samples (based on colony-forming units, or CFU, per square inch), and the results will make you eternally grateful for hand sanitizer.

Overall, the study found that the average hotel room is dirtier than a typical home, an airplane and even a school.

The dirtiest surface in the nine hotel rooms tested was the bathroom counter (1,288,817 CFU/sq.in.), followed by the remote control (1,211,687 CFU/sq.in), the desk (604,907 CFU/sq.in.) and the phone (4,252 CFU/sq.in.).

Perhaps most surprising is that the three-star hotels in the study appeared to be the least germ-ridden compared to basic one- and two-star accommodations as well as higher-end four-star hotels. For instance, the dirtiest surface in a three-star hotel room was the bathroom counter with an average of 320,000 CFU/sq.in. – approximately EIGHT times less than a four-star hotel room and three times fewer than a five-star hotel room.

And even though four-star hotels often come with added luxuries, they also come with more germs, at least according to this study. In the four-star hotels that were tested, the bathroom counter was the most bacteria-laden surface – in fact, it was the single dirtiest surface among all spaces.

Though it’s impossible to avoid germs, there are ways to reduce health risks associated with germs. Hand washing has been found to reduce the risk of respiratory infections by 16%. So remember, the next time you check into a hotel, wash your hands frequently, disinfect surfaces and never, EVER eat on the bathroom counter