After a long day, few things feel better than slipping into a freshly made bed. But while your sheets and pillows may feel clean and comforting, they can quietly become a thriving home for bacteria, fungi, mites and other microscopic organisms.
We spend roughly a third of our lives in bed, and during that time our bodies shed sweat, saliva, oils and millions of dead skin cells. For microbes, this combination of warmth, moisture and food creates the ideal environment to grow.
Dust mites are one of the most common inhabitants of bedding. These tiny creatures feed on dead skin cells and multiply rapidly in mattresses, pillows and duvets. While they don’t bite, both the mites and their waste can trigger allergies, asthma and eczema in sensitive people.
Bacteria are also common on bed linen. Research has shown that unwashed sheets can carry high levels of skin bacteria such as Staphylococcus. While many of these microbes are harmless, some strains can cause skin infections or more serious illness if they enter the body through cuts or weakened immune systems.
Hospitals take bedding hygiene seriously for this reason. Studies of hospital linen have found harmful bacteria such as E. coli and other pathogens on unwashed sheets. In some cases, even viruses have been detected, with evidence suggesting that changing contaminated bedding can release infectious particles into the air. This is why hospital laundry is washed at very high temperatures and changed frequently.
At home, the risk is generally lower, but that doesn’t mean bedding is clean. One analysis of a pillowcase that hadn’t been washed for a week found millions of bacteria per square inch—far more than what’s typically found on a toilet seat. Pillows, in particular, are a problem because they are rarely washed and absorb sweat from the head night after night.
Fungi can also flourish inside pillows. Studies examining used pillows have found large amounts of fungal spores, especially Aspergillus fumigatus, a species commonly found in soil. The warm, damp conditions created by sweat, combined with food from dust mites, allow these fungi to survive for years. Fluffing pillows can release spores into the air, where they may be inhaled.
For most healthy people, this exposure doesn’t cause harm. However, individuals with asthma, sinus problems, lung disease or weakened immune systems may be more vulnerable. In rare cases, fungal infections can become serious and even life-threatening in people with compromised health.
Washing pillows doesn’t always solve the issue, as some fungi can survive normal laundry temperatures and excess moisture may actually encourage further growth. Experts often recommend replacing pillows every couple of years, or much sooner for people with respiratory conditions.
When it comes to sheets and duvet covers, most specialists advise washing them at least once a week. Using hot water helps reduce microbial build-up, and ironing can further lower bacterial levels. Extra care should be taken if someone is ill, if children wet the bed, or if pets regularly sleep on the bedding.
Lifestyle habits also matter. Going to bed without showering, sleeping in dirty clothing, wearing makeup overnight, or eating in bed can all increase the amount of bacteria and fungi on your sheets. Allowing pets onto the bed adds another layer of microbial exposure.
While it’s impossible—and unnecessary—to eliminate every microbe, regular washing can significantly reduce buildup and improve sleep hygiene. For most people, weekly laundering is sufficient, but in some cases, more frequent cleaning may be wise.
A clean bed won’t make your home sterile—but it can make it a healthier place to rest.
