Drying laundry in the home poses a health risk to those prone to asthma, hay fever and other allergies, according to new research.
A study carried out by the Mackintosh School of Architecture found that many homes had too much moisture indoors.
Up to a third of this moisture was attributed to drying laundry.
The researchers have called on housebuilders to build dedicated drying areas into new housing to address the health concerns.
A study of 100 homes by the Mackintosh Environmental Architecture Research Unit in Glasgow found 87% dried their washing indoors in colder weather.
Researcher Rosalie Menon said people were not aware how much moisture this added to the air.
She said: "Going into people's homes, we found they were drying washing in their living rooms, in their bedrooms.
"Some were literally decorating the house with it, but from just one load of washing two litres of water will be emitted."
A total of 75% of households, which were of mixed styles, had moisture levels which could lead to dust mite growth.
There was also a strong association between drying laundry and mould spores.
A particular mould spore known to cause lung infections in people with weakened immune systems was found in 25% of the homes sampled.
The research, funded by the Engineering and Physical Sciences Research Council, was the first to track the implications of drying laundry passively inside the home.
All of the types of housing surveyed had a lack of suitable spaces for drying clothes.
The researchers want to see dedicated drying areas incorporated into new housing.
Ms Menon said: "These spaces should be independently heated and ventilated. It's very much going back to the airing cupboards we saw in more historical types of housing."