A week is enough time for bedding to collect sweat, dead skin cells, and allergens from dust mites. Yet, many people wait nearly a month before washing their bedding. Regular washing addresses a real hygiene concern, one that most people underestimate in terms of frequency. In late September 2026, allergologists and microbiologists gathered by Popular Science to discuss the importance of washing bedding more often than most people do. On average, people wait nearly 24 days before changing their bedding, giving an invisible ecosystem time to develop. Washing bedding is more about hygiene than aesthetics, as sweat, dead skin, and mites accumulate night after night. The bed is far from a sterile environment. Each night, a person can release up to a quarter of a liter of sweat and shed hundreds of thousands of dead skin cells—nearly 1.5 grams per day. Along with sebum and cosmetic residues, this organic material gets absorbed into the fabric, invisible but very real. This organic matter feeds a population of microscopic dust mites, whose waste is among the most common allergens in homes. Alongside them, millions of bacteria and fungi thrive, and used pillows can even host molds like Aspergillus fumigatus. Warm and slightly damp, bedding provides an ideal habitat for these microorganisms. For many people, these microorganisms can have real health consequences. According to allergologist Sandra Ho, dust mite allergies affect about 20 million people in the United States alone, causing symptoms like sneezing, a stuffy nose, itchy eyes, or asthma attacks. In people with sensitive skin, these microorganisms can worsen eczema, the red, itchy patches that appear on the skin. In severe cases, these reactions can lead to sinus infections or even trips to the emergency room. These issues become more severe when bedding remains unwashed for more than two weeks. To combat this buildup, specialists recommend a simple schedule. Sheets and pillowcases should be washed in the machine once a week, more frequently in cases of heavy sweating, illness, or pets in the bed. Towels, which stay damp for long periods, follow the same rhythm. Pillows themselves should be washed thoroughly once or twice a year. Washing at 60 °C or higher is significantly more effective at killing mites and bacteria, recalls microbiologist Primrose Freestone. A simple habit can also help between washes—leaving the bed unmade upon waking allows the sheets to dry and deprives mites of the humidity they need. However, this practice is often overlooked, as the average sleeper waits nearly 24 days before changing their sheets and up to 25 days for their pillowcases. Some even delay washing until once or twice a year. Reducing this delay to a week is enough to significantly reduce this invisible burden.