“…Acquired TN is the result of excessive or repeated trauma caused by frequent application of hair permanent liquid, hair dyes, frequent brushing, scalp massage and lengthy and repeated ultraviolet exposure. In 1966, Owen and Chernosky proved that TN can also be caused by repeated trauma inflicted by a laboratory apparatus designed to administer controlled stress 1 . Fifty‐three samples of normal‐appearing scalp hair were used, some taken from healthy subjects and some from patients with TN.…”