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 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 three times max," Philip Tierno, a microbiologist and pathologist at the New York University School of Medicine, told Tech Insider.
And this is assuming you're hanging it somewhere dry so 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 microbes 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 neutral 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.
The uncomfortable truth about how often you should wash your bed sheets
When you settle in for the night, the last thing you probably think about is what may be lurking in the nooks and crannies of your bedding.
And your ignorance is most likely bliss, because it turns out, beds are ripe — pardon the pun, hotbeds — for microscopic life.
"You have spores of fungi, bacteria, animal dander, pollen, soil, lint, finishing agents of whatever the sheets are made from, coloring material, all sorts of excrements from the body including sweat, sputum, vaginal, and anal excretions, urine milieu, skin cells ... " Philip Tierno, a microbiologist and pathologist at the New York University School of Medicine, told Tech Insider. "Plus there are cosmetics that people use — they put oils and creams on their body, all of that is in that milieu."
And there's a lot more, Tierno said, "including food by the way, people eat in the bed. That of course provides a nice environment for these organisms."
Your home's environment is so nice, in fact, that scientists all around the world are trying to identify and quantify the diverse array of pollutants and allergens that not only shack up in your bed, but fawn out across an entire household. These domestic microbes may negatively (or sometimes even positively) affect our health. Nasty bacteria from raw meat and vegetables, for example, can live on surfaces for days or even years and cause horrendous cases of food poisoning. Mold on bathroom surfaces and damp cloths can exacerbate or cause allergies and asthma.
Think this doesn't affect you because you're a relatively clean person? Think again. Humans naturally produce 26 gallons of sweat in bed every year. This moisture, at high humidity, is an "ideal fungal culture medium."
In a 2015 study that assessed the level of fungal contamination in bedding, researchers found that feather and synthetic pillows 1.5 to 20 years old can contain between 4 and 17 different species of fungus.
And over time, Tierno said, the amount of fungi, bacteria, and many other debris that accumulate is dramatic.
"You know how Rome was covered and we excavated to find out Rome? That's because gravity [causes debris] to settle over time and bury things," Tierno said. "The same thing happens with mattresses and pillows: Gravity brings down all this debris and it settles in the core of the pillow and the mattress. And you’re inhaling that debris 8 hours a day."
Considering that 1 in 6 people have allergies, Tierno says, and the average person spendsabout a third of their life in bed, scientists are speculating that our beds may be the source of our misery.
"I didn't even mention the dust mites," Tierno said. "There are dust mite feces and dust mite debris, which are allergens. Even if you don't have an allergy, you react to it as a normal person."
These allergens may cause you to wake up with a stuffy nose, cause or exacerbate allergies, or aggravate asthma.
Therefore it's imperative to keep your bed relatively clean, Tierno says, so that you don't overexpose your body to these allergens.
So how often should you wash your bed sheets?
"Stuff like that accumulates to become significant usually between 1-2 weeks," Tierno said."Bottom line, they should be washed probably on the average of once a week."
And while there aren't any formal studies on how often you should be cleaning things in your home, Tierno says, this weekly sheet washing suggestion is just a recommendation.
"Certainly if you go one week and two days you're not going to get arrested," Tierno said.
And if you're like most people and have a hard time wrestling with washing your duvet cover, do not fret. You only have to wash that periodically, about every six months, Tierno says, depending on use.