Your bed gathers all sorts of dirt, oil, and sweat while you sleep. Learn how often to wash bedsheets so you can sleep soundly on fresh bedding. You typically spend upwards of eight hours in bed each day, which leads to the buildup of dirt, body oils, dead skin cells, sweat, and other grime on your sheets and bedding. All this residue isn’t just gross to think about; it can also provide fodder for dust mites, put extra strain on the fabric’s fibers, and trigger health issues including allergies, skin irritation, and acne—not exactly ideal for a peaceful night’s sleep.

The average person changes their sheets about every 24 days, according to a recent survey by Mattress Advisor. But that’s not the best schedule for optimal hygiene and freshness. How often you should wash your sheets depends on a few factors, but there are some general rules that work for most people. Read on to learn exactly how often to wash your sheets, as well as how to preserve their freshness if you decide to bend the rules a bit.

Washing your bed linens roughly once a week keeps them fresh on a consistent basis. Plan to include this task in your weekly cleaning plan to help encourage the habit. Remember that you don’t have to wash linens the same day you strip your bed. Having a few alternative sheet sets on hand allows for quick swaps.

While once a week is a decent rule of thumb, the frequency with which you should wash your linens is determined by how rapidly they become dirty. For example, if you travel frequently and don’t sleep in your own bed every night, you can probably go a little longer without washing. On the other hand, if you or your sleeping partner sweat a lot while sleeping, or if you share a bed with a pet, your linens will get dirty much faster. Allergy sufferers and those with sensitive skin may want to replace their bedsheets more frequently, such as every three or four days.

If washing your linens weekly (or more regularly) isn’t an option, there are a few things you can do to extend the duration between washes. First, wash your face and take a bath or shower before going to bed to lessen the amount of filth, oil, and sweat you bring with you. Consider having your pet sleep somewhere else to prevent hair and dander from getting on your bedding, and avoid munching in bed. Owning numerous sets of sheets will also make this task easier, as you can just switch out your bedding and put the laundry away for another day.