Sleep shows on your face, and it has been measured

Researchers have photographed people after normal sleep and after restriction, then asked strangers to rate the faces. The sleep-deprived versions were consistently rated as having darker circles under the eyes, more hanging eyelids, paler skin and more visible fine lines. Observers also rated them as sadder and less healthy — without being told anything about sleep.

A separate study followed self-described poor sleepers and good sleepers. The poor sleepers scored higher on measures of intrinsic skin ageing, and their skin barrier recovered more slowly after being deliberately damaged.

None of this is about a mask. It is about sleep. But it is the reason the mask matters.