16th April 2026
According to RNZ’s Sunday Morning, what ends up in your bed each night may be more confronting than many people realise. Professor Primrose Freestone, a clinical microbiologist at the University of Leicester, says the average person releases up to 300 millilitres of sweat into their sheets overnight. This happens regardless of the weather. Alongside this moisture, the body sheds skin cells that quickly become a food source for dust mites.
Freestone explains that these conditions create an ideal environment for bacteria and microscopic life to thrive. Over time, beds can accumulate a mix of sweat residue, skin debris, and microorganisms that affect hygiene.
This has direct implications for daily routines. While many people prefer to shower at night, Freestone suggests this may not be the most effective approach for staying fresh. She explains that going to bed clean does not guarantee waking up clean. A bed that has not been washed regularly can transfer bacteria and dried sweat back onto the skin during the night. As a result, people may wake up feeling less fresh than when they went to bed.
A morning shower helps address this issue. It removes sweat, bacteria, and any residue picked up from bedding overnight. Freestone says this can leave people feeling cleaner throughout the day and reduce body odour caused by bacteria breaking down sweat.
Sheet washing habits also play a key role in maintaining hygiene. Freestone recommends washing sheets once a week under normal conditions. During warmer months, when sweating increases, she advises washing them every three to four days. Without regular washing, beds can become what she describes as a dense microbial environment.
Dust mites are a particular concern, especially for people with asthma. According to Freestone, it is not the mites themselves that cause problems but their waste products. These particles can trigger allergic reactions and respiratory issues in sensitive individuals. Pillows tend to harbour high concentrations of mites due to prolonged contact and moisture.
To reduce these risks, Freestone advises washing bedding at higher temperatures. Cotton sheets can be safely washed at 60 degrees Celsius, which is effective in killing most microorganisms. She notes that many bacteria that live on human skin thrive at lower temperatures, so hotter washes are needed to properly sanitise fabrics.
For pillows, washing at the same temperature is ideal when the material allows. If washing is not possible, placing pillows in a freezer for a day can help kill dust mites. This provides a practical alternative for items that cannot be laundered easily.
Freestone also highlights that cold washing alone may not be sufficient unless a disinfectant detergent is used. For those seeking an extra level of cleanliness, ironing sheets can further reduce bacteria. The heat and steam from ironing can eliminate remaining microorganisms and improve overall hygiene.
Clean bedding and thoughtful routines have a direct impact on personal hygiene. Regular washing, combined with a morning shower, can help reduce exposure to bacteria and allergens. It also supports a fresher start to the day.
