The louse is found in some medieval encyclopedias. It is a small worm that is generated from the human body, either from sweat or from the pores. The usual remedy for lice is to boil quicksilver (mercury) in olive oil, then wear a woolen girdle (belt) soaked in the mixture. Egg white or butter and mercury is also said to be effective. (This is definitely not recommended; mercury is toxic!)

The human body louse is the species Pediculus humanus.