‘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.
