Get ready to be grossed out, because we've got some bad news. Everyone knows they're supposed to wash their sheets, but when things get hectic, changing the bed linens honestly just doesn't seem that important. But it is—trust us on this one.
1. Acne breakouts. Even if you wash your face before bed, your skin creates natural oils that cling to your pillowcase. So when you're sleeping on the same pillowcase night after night, you're just transferring yesterday's oil onto tonight's face. Yuck! Switch out your pillowcases often and you'll probably see a reduction of acne breakouts.
>> Read more: 3 Super Easy DIY Skin Scrubs
2. Infections & allergies. All the nasty germs you pick up throughout the day, like cold viruses, fungi (athletes foot) or the flu, could transfer onto your sheets and live for weeks. Scientists have found that over the course of a year, there are 100 liters of sweat that seep into your bed sheets. The longer you sleep in your own filth, the higher your chance of developing allergies.
Philip Tierno of the New York University School of Medicine explained it this way: “Stuff like that accumulates to become significant usually between one or two weeks." Gross? We certainly think so.
>> Read more: The 11 Germiest Spots in Your Home That You're Not Cleaning
3. Pet waste. Dogs and cats drag all kinds of yucky stuff into the house, like pollen, dirt, worms and insects—even Lyme disease—so think twice before you let them jump into your bed.
Marilyn C. Roberts, a professor of environmental and occupational health sciences at the University of Washington told Yahoo! Health, "Dogs, by nature, are not hygienic,” stresses Roberts. “You can wash them every week, but they still go outside and sniff other dogs, so they can pretty much bring in anything."
"Pets should be pets — they should have their own bed because they can be a reservoir for human diseases,” states Roberts. “Or you can give your pet a disease, like MRSA, and then the pet can give it back to you."
The bottom line is this: wash your sheets every seven to 10 days, or risk the (gross) unexpected consequences. Remember, you wouldn't wear the same clothes for a month without washing them, so you shouldn't sleep in the same sheets for a month either!