I hate to break it to you, but your bath towel is dirty — like, really dirty.

The moment you use it, it becomes a breeding ground of bacteria; fungi; dead skin cells; salivary, anal and urinary secretions; and many other germs lingering in your bathroom that may have hopped onto your towel — including droplets from your toilet.

While most of these microbes aren’t likely to harm you, given that most of them probably came from your own body, they’re there, and they’re multiplying quickly.

So how many times can you use your towel before before concentrations of your own flora get so out of hand that you need to wash it? “If you can dry it completely, no more than 3 times max,” Philip Tierno, a microbiologist and pathologist at the New York University School of Medicine told Tech Insider.

And this is assuming that you’re hanging it somewhere dry so that it can completely air out. “A damp towel is growing,” Tierno said. “If there is odor coming from the towel, wherever there is odor, there are mircobes growing so it should be washed.”

Towels serve as ideal breading grounds for germs because they contain many of the requirements for microbial life: water, warm temperatures, oxygen, food, and a netural pH. The human body supplies these ideal living conditions, which is why our entire body is covered in them inside and out.

When you wick moisture from your body, the microbes and other secretions such as cellular debris that live on the surface of your body get deposited onto your towel. Your cellular debris and other deposits from the air serve as food for the microbes, and the moisture supplies water at a neutral pH.

But it’s hard to say whether the microbes growing on your towel are harmful, Tierno said, since most germs in our households aren’t dangerous.

But if you share your towel with others, you could potentially come into contact with organisms that your body isn’t used to dealing with — such as Staphylococcus aureus, Tierno said, “which may give rise to a boil, or a pimple, or an infection.”

“The idea is to be prudent and to be aware,” Tierno said. Mostly, aware that your towel is disgusting. And you’re probably not washing it enough.

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