I work closely with Americans, and it’s become apparent that they have a strange obsession with sweat and skin expressions.  I don’t know why.

Sweat: Consider these expressions they use on a regular basis about a rather distasteful human feature: ‘sweat equity’, ‘break a sweat’, ‘break into a cold sweat’, ‘don’t sweat it’, ‘sweat like a pig,  ‘sweat like a sinner in church’, ‘sweat something out’, ‘the sweat of (one’s) brow’, ‘without breaking a sweat’, ‘work up a sweat’, ‘don’t sweat the small stuff’.

Skin: Likewise with skin: ‘have skin in the game’, ‘save one’s own skin’, ‘no skin off my back‘, ‘by the skin of your teeth’, ‘skin deep’, ‘no skin off your nose’, ‘save one’s own skin’, ‘make flesh crawl’, ‘thin skinned’, ‘all skin and bone’, ‘get under someone’s skin’, ‘more than one way to skin a cat’.