‘This 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.”
Craythorne says central heating can cause these reactions because it creates a warm but very dry environment, especially if it’s been on hot all day with no ventilation. But she says it’s not the only culprit for irritation in the winter. Cold outdoor air can be even more drying as it naturally holds less moisture – and wind makes things worse by speeding up the evaporation of both water and the skin’s natural oils.
“Some people are more susceptible than others,” she says, “particularly those who have eczema or rosacea.”
She says that if you are struggling with irritated skin in the winter, it can help to keep central heating a little cooler and to use a humidifier. Be gentle with your skin: avoid harsh soaps and opt for creamy, soap-free cleansers. Use a fragrance-free moisturising cream that contains occlusives to slow water loss, alongside ingredients such as ceramides and glycerin to support the skin barrier and draw in moisture. “Think of it as putting a little blanket on your skin for the winter,” she says.
