Hair care
Scalp hair grows, on average, at a rate of about 1.25 centimeters per month, and shampoos or vitamins have not been shown to noticeably change this rate. Hair growth rate also depends upon what phase in the cycle of hair growth one is actually in; there are three phases. The speed of hair growth varies based upon genetics, gender, age, hormones, and may be reduced by nutrient deficiency (i.e., anorexia, anemia, zinc deficiency) and hormonal fluctuations (i.e., menopause, polycystic ovaries, thyroid disease).
Hair theft
This created a highly profitable market in human hair, which was said in the mid-19th century to be worth twice its weight in silver. In 1851 of hair was imported from France to England with a value of £3,621 (£ today). "The Hairdressers' Journal" reported in May 1863 that a hundred tons of hair a year was being sold in Parisian markets. Not all hair was created equal; female hair from northern Italy and Spain was especially prized for its glossy blackness and curliness. It retailed at a price of 10–12 shillings per ounce (worth about £43/€50/$67 in 2013 prices), rising to £1 per ounce (about £87/€101/$136) for very long hair. A "hair harvest" was held annually in the poorer villages of Italy, where local girls sold their hair to wig-makers. One observer of a hair harvesting event reported seeing "several girls, sheared, one after the other like sheep, and as many more standing ready for the shears, with their caps in their hands, and their long hair combed out, and hanging down to their waists."