Especially single men.

In one survey, 55% of single men between 18 and 25 reported changing their sheets only four times a year.

And to be clear, those are beds that you would not wanna sleep in.

You shed about 15 million skin cells each night, but they don't just pile up in your sheets.

Because something else is already there waiting to gobble them up: dust mites.

And the longer you wait between washes, the more food these critters will have and the more they'll procreate and multiply.

So if you don't wash your sheets, you'll be sleeping with hundreds of thousands of arachnids.

Now, for the estimated 20 million Americans with dust allergies, it gets worse.

Dust mites and their feces produce proteins that cause red and itchy eyes, runny noses, and other cold-like symptoms in people who are allergic.

And dust mites, well, they're actually not the only allergen in a dirty bed.

If you never wash your pillow sheets, a community of fungus can also build up there.

One study found that a typical pillow has as many as 16 different species of fungus and literally millions of fungal spores.

And the most common among them, Aspergillus fumigatus, is potentially dangerous.

In addition to allergic reactions, it can infect your lungs and other organs.

And it's not just fungi joining the party.

You see, bacteria also love a good unwashed pillow case or sheet a lot.

Another study found that unwashed pillow cases and sheets had up to 39 times more bacteria than pet-food bowls and several thousand times more bacteria than a toilet seat.

Like Staphylococcus aureus, which in some rare cases can be deadly.

Now on a slightly less or perhaps more frightening note, dirty sheets can also give you acne.

Each night, the oil, lotion, and other cosmetics on your skin transfer to your sheets and build up over time until eventually your bedding is basically a giant used makeup wipe.

Then during the following nights, all that gunk transfers back onto your body, clogging your pores, and, viola, you've got acne.

Fortunately, there's a simple way to avoid all of these problems.

Wash your sheets, and wash them often.

Experts recommend about once a week using the hottest water possible.

That'll kill a lot of bacteria and dust mites, get out stains, and remove oils.

Plus, as awful as making your bed might be, there's simply nothing better than slipping between clean, crisp sheets.