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Some hotels have raised the bathtub to an art form. It’s understandable that after a long day of travel you just want to drop into a bubble bath with a glass of wine. Before you do, though, a word of caution. As you may know, hotel bathrooms —even at five-star hotels—can be dirtier than airplanes, which is probably not what you want to be thinking about while luxuriating in the tub.

According to microbiologist Philip M. Tierno, who spoke with Real Simple, no matter how gorgeous the tub, you may want to skip taking a bath entirely, due to something called biofilm. He describes biofilm as “a nearly undetectable layer of bacteria that sticks to tubs and other surfaces. It comes off only with vigorous scrubbing with a hard-bristle brush and soap.”

Similarly, even if the tub looks spotless, you still may want to avoid soaking in it, because the very tools that may have been used to clean the tub may be harboring germs. A 2012 study published by the Journal of Microbiology, found that an incredibly high number of germs were found in hotel housekeepers' cleaning supplies, including sponges and mops.

WATCH: 7 Ways to Avoid Germs During a Hotel Stay

That’s not all, either: A study by the travel logistics website TravelMath. found that hotel rooms are dirtier than the average airplane or school and you wouldn’t strip off your clothes in either of those places, now would you?

Of course, not all bacteria or viruses will make people sick. As Time notes, we all come into contact with thousands of germs every day, and only a small percentage are ever dangerous. So, if you want to risk it and soak in that glorious Jacuzzi tub in your hotel room, Real Simple suggests squirting shampoo in the tub and run the water on hot for a minute to decrease the number of germs present—or bring your own supply of disinfectant.

Instead of soaking in that tub, some experts suggest sticking to the shower and instead using the tub to store your luggage.