Blushing occurs when one is embarrassed.
Blushing is more common in the young than in the old, and in women compared with men.

Blushing is due to dilatation of blood vessels in the face, transmitted through the sphenopalatine ganglia by parasympathetic nerves, which indicates that blushing occurs when one feels safe.

Blushing signals that one cares about how one is perceived by others.
Blushing signals that one wants to be with who one is with.
Blushing conditions partnerships and group membership.