I've recently been reading The Saga Of Ragnar Lodbrok in translation online,due to my love of Norse myths and legends (they have awesome heroines, and I'm something of a feminist, as well as a fantasy writer)   and in the first part, there's something which struck me. When Ake and Gríma, the impoverished foster parents of the heroine Aslaug, find her hidden in the harp with a lot of money, Gríma plans to change Aslaug's name to Kraka, or "crow", shave off her hair and rub tar in her scalp in order to prevent the hair from growing and pass her off as the pair's biological daughter.

Does tar in the scalp really prevent hair from growing, or was that just invented by the storyteller?