UK households are being urged to stop drying towels outside - because of a quirk of science which causes them to become rough and abrasive.

Battling with scratchy, sandpaper-like towels is one of life's little irritations, especially when it feels like you're spending half your life battling through piles of washing and laundry and constantly trying to dry all your clothes and towels - only for them to end up stiff and uncomfortable to use. But there is a real reason, spotted by Reddit and proven by science - and it's all to do with drying them outside in the air.

One poster on Reddit's r/AskUK said: "Why are old people's towels always dead hard?"

It turns out, it's not actually a mystery, and in fact the phenomenon of the coarse, super-rough towel is not limited only to older people but can happen to anyone at any age - because it's all about how you dry them.

In response, one user said: "Definitely the tumble drying vs line drying. As someone who WFH most of the time, I am fortunate enough to be able to line dry my clothes much of the time. It's better for the environment and better for the fabric.

"However, it can definitely make the towels a little crisp. You CAN use laundry conditioner but 1. Ain't nobody got time for dat and 2. After the first use the towel is fluffy again, so unless you use a towel once then launder it, what's the difference?"

Another added: "Air dried instead of tumble dried. I actually asked my father about it. He has since passed away when he gold told he was obsessed with drying his towels outside. He told me that he likes the feeling of the towel being scratchy. I was perplexed because when I get out of the shower or bath I want a comforting, soft towel."

According to How Stuff Works, there is a scientific reason why air dried towels - ie those dried outside in the air - are rougher.

It explains: "Drying your laundry outside in the sunshine feels wholesome, doesn't it? It's a simple thing you can do to save energy (those clothes dryers really the kilowatt hours) and sun-dried fabric just smells good. But there are some items of laundry for which air drying does no favors, and one of them is the .

"When it comes right down to it, most fabrics (with the exception of silk and wool) that aren't made out of plastic are made out of plants. Cotton is made from the fluffy seed casing of a small shrub, while rayon, modal, viscose, acetate, bamboo fabric and the like are made out of wood pulp. Plants contain a lot of cellulose, an organic compound that helps keep plant cell walls stiff. Cellulose is great at absorbing water, which is why we make towels out of cotton instead of polyester.

"Water molecules cling to cellulose and climb along it through a process called capillary action - cellulose can even defy gravity in order to pull the water along its surface.

"Because water is a polar molecule, meaning one side of it holds a more positive charge and the other end a more negative charge, water is easily seduced by electrical charge. In the study published in the February 2020 issue of The Journal of Physical Chemistry C, the research team found that individual, cross-linked fibers on air drying fabric like a cotton towel actually have "bound water," or water that behaves in unique ways as it adheres to the surface of something because it likes the charge of that thing, which gets sandwiched between the fibers, causing them to stick together."