BoM/TWS Message Forum

You can use blood. It’s not anything special about hair that necessitates it’s use in the spell, it’s just a way of getting the person’s essentia into the golem. You could use blood, hair, semen, or even fingernail clippings according to "Bits and Pieces, and How to Get Them Off People" . I assume the spell ingredient list just specified hair because most of the characters in the story wouldn’t understand what essentia is.