turn a hair

Verb

turn a hair (third-person singular simple present turns a hair, present participle turning a hair, simple past and past participle turned a hair)

1. (idiomatic) To show fear, alarm or distress; to be affected (by an experience or situation).
   • If in some hideous dissecting-room or fetid laboratory you found this man lying on a leaden table with red gutters scooped out in it, you would simply look upon him as an admirable subject. You would not turn a hair.1891, Oscar Wilde, “chapter 12”, in The Picture of Dorian Gray, London; New York, N.Y.: Ward Lock & Co., →OCLC
   • […] those seasoned topers who drank their companions under the table without themselves turning a hair […]1917, Henry Handel Richardson, Australia Felix, New York: W.W. Norton & Co., Part IV, Chapter 9, p. 435