Ja.
Från Pottermore :
The Polyjuice Potion, which is a complex and time-consuming concoction, is best left to highly skilled witches and wizards. It enables the consumer to assume the physical appearance of another person, as long as they have first procured part of that individual's body to add to the brew (this may be anything - toenail clippings, dandruff or worse - but it is most usual to use hair). The idea that a witch or wizard might make evil use of parts of the body is an ancient one, and exists in the folklore and superstitions of many cultures.
Blod och saliv är verkligen kroppsdelar.