We usually wash clothes when they have been worn for a long time and are no longer fragrant and fresh, or when they show a slight fading caused by several days of wear. But few people know how often such bed linen should be washed. That is to say, the fabric in which we spend even a third of the day – if we keep to the recommended eight hours of sleep. And hand on heart – most of us wash our bed linen less than we should. What can cause this? That we sleep in something that can literally make us sick to our stomachs.
How often you should wash your bedding depends on many factors. Sheets, duvets and pillows are in close contact with your skin all night, so you should wash them all equally often. But of course it depends on whether it’s summer, how much you sweat or if you’re ill.Standard bedding
Pillowcases and duvet covers are the bed linen that we are in direct contact with every night. Changing and washing should be regular, ideally at intervals of two to four times a month, depending on the season.
Think about the fact that every night you leave sweat, hair, and dead skin in your bed, which is a delicacy for microscopic insects such as dust mites. And if you’re allergic, your symptoms may be exacerbated by unwashed bedding. It’s best to wash such bed linen at least at 60°C and then tumble dry or iron properly. We recommend that you do not fill the washing drum completely full so that the bed linen is washed perfectly. If you smell an odour instead of fresh laundry after drying, the linen has not been washed properly and contains body fluids.

Pillows and duvets
If you use pillow and duvet protectors, just wash them every four months. On the other hand, the protectors themselves should be washed at least once a month. If you don’t have the protectors, you should wash the duvet covers once every three months or even sooner. Pillows, on the other hand, should be washed every month. The pillow is the riskiest and dirtiest part in your bed. Don’t grow mites under your head, it only takes a moment to undress and go to the washing machine, plus your health will thank you.
Mattress protector
The mattress protector has a very important role, for example, thanks to the protector, sweat will not penetrate into the core of the mattress – by the way, you sweat up to a liter of sweat overnight. This level of sweat is individual and again depends on the room conditions and the health of the individual. They also prevent contamination, deterioration and a large number of dust mites in the mattress. The protector itself should be washed at least once a month. If there is a spill of liquid from a good cup of tea – who wouldn’t enjoy a good breakfast in bed – promptly remove the cover to keep the mattress clean.
Source: https://www.cnet.com/how-to/do-you-wash-your-sheets-enough-probably-not/