Dry air indoors can cause an inflammatory reaction, yet so can cold, windy outdoor conditions – but turning down the heating and using a moisturising cream can help
‘T
his is kind of true,” says consultant dermatologist Dr Emma Craythorne. Human skin has evolved to retain water, thanks to a protective barrier on its surface. But that barrier isn’t totally watertight. Water is constantly moving across it, depending on the humidity of the surrounding air.
Skin tends to be most comfortable at a relative humidity of about 40%. When the air around us is drier than that, water is more likely to leave the skin. That matters because the process of water escaping across the skin barrier is mildly inflammatory.
“The skin becomes drier,” says Craythorne. “Your blood vessels become a little bit more dilated, making skin look red. Cytokines are stirred up, which are little proteins that set off more inflammatory reactions but also irritate our nerve endings. Things might feel more itchy.”
