Even if you sleep alone, you aren't really alone in bed — you've got the company of millions of dust mites. They're nestled in next to you and under you, burrowed into your mattress, the sheets, the blankets and yes — they're even in the pillows and pillow cases.

It's likely that they've burrowed into your PJs as well.

Aside from being gross, those millions of mites aren't too good for your health, either. They won't make you violently ill, but you should evict them from their comfy homes nevertheless.

The mites play a role in producing "sick bed syndrome," according to Dr. Lisa Ackerley, a home hygiene expert. The syndrome can lead to respiratory issues, unexplained coughs and running noses, as well as symptoms many mistake for allergies. Ackerley, who estimates there are about 10 million mites in every bed, said mites are proliferating — houses are now better sealed against the winter elements, with rising humidity.

"Dust mites like warm, moist environments — the bed's the perfect environment," she explained. But this next statistic will likely have you running from the bedroom: 10 percent of the weight of your pillow could be dust mites and their droppings.

"They can cause rhinitis, a cough, dry eyes. They can disturb sleep. People with other allergies can have them made worse," added Ackerley. The dust mites are likely a factor in 80 percent of asthma cases.

And it seems dust mites are pretty hardy against things like a laundry wash or even the human common cold.

So how do you evict dust mites from your sleeping sanctuary? Well, wash those linens separately and regularly – at least once a week – to kill bacteria and the mites. Be sure to use a laundry disinfectant if the water can't reach at least 60 degrees.

While you're doing the wash, open the windows, even if it's cold. Lower the temperature and humidity, which is something mites relish. Then it's time to vacuum the mattress, floors, and anything else where mites may be bunkered down.

And whatever you do — don't go hunting down photos of bed mites on the Internet. Once you see them under the microscope, you'll never be able to sleep soundly in your bed again.