While replacing your sheets and pillowcases is second nature, replacing your mattress (or refreshing your mattress topper) is just as important. Take it from New York University microbiologist Philip Tierno, who hasn't slept without some sort of mattress protector in 25 years.
"You know how the Roman empire got buried over time, and all those remains are now quite a few feet below ground and they have to excavate?" he asked Business Insider. "In a similar fashion, debris that is found in and on mattresses—especially in the interior—builds up."
And now for the graphic explanation: "When you're in the bed you desquamate, or you slough off tissue, and all that cellular debris collects between your sheet and the sheet over the mattress," explains Tierno. "That serves as food for dust mites. They eat human tissue. And they defecate and excrete substances and then they die. And that's part of the allergens that collect. In addition you have bodily secretions of all types." Long story short: You can get sick if you don't replace your mattress or mattress protector on the regular.
Fortunately, the solution is simple: Invest in a waterproof mattress protector, like this top-rated pick from Amazon ($20). From there, you "don't have to change it ever—only when it becomes mechanically dysfunctional," he clarifies. A good rule of thumb is to replace your mattress when an indent forms where you normally sleep, or when the firmness begins to give out.
Head over to Business Insider for more from Tierno, and share your favorite mattress protector with us in the comments.