You won’t sleep soundly after this.

An unwashed pillowcase could harbor 3 million bacteria after just one week, which is about 17,000 times more than a toilet seat, according to a report Amerisleep shared this month.

The analysis included cleanliness data for mattresses, linens and pillowcases, as well as a breakdown of the potential pathogens lurking between the sheets.

Allergens, fungi, dander and dead skin are among the unsettling particles you wouldn’t want to cozy up with at night — and they can attract dust mites, microscopic critters that feast on sloughed skin cells.

Experts warn that pillowcases, specifically, should be changed routinely — and more than just once a week (or month).

“When you get into bed, you contaminate your bed linens with dead skin cells (about 50 million per day), sweat, makeup, lotions, hair, and anything else you’ve picked up during the day, from pollen and pet dander to fungal mold and dirt particles to bacteria and viral particles as well,” Dr. Hadley King told Well+Good. 

“Dead skin cells and sweat provide food for dust mites, attracting them to your bed and helping them multiply.”

A recent TikTok gave a visual representation of the bacteria colonies that apparently flourish beneath your head every night.

Marketing the silver-infused, acne-fighting pillowcase brand Argie, user @simonandbee cut off a corner of a regular pillowcase and placed it in a petri dish, showing the alleged bacteria and fungal growth over time.

After just a few days without washing the pillowcases, bacteria quickly formed, the creator alleged.

The revelations come after years of research on soiled sheets.

In fact, past studies have shown that disease-causing bacteria live in unwashed bedsheets.

Despite the good doc’s warnings to routinely change pillowcases every few days and sheets every week, some unbothered sleepers wait a month or more to launder their bed linens.

A survey from the UK discovered that nearly half of men wait up to four months to change their sheets, with some only washing them when they remember.

Unsurprisingly, their bedding was changed more often when they were in a relationship.