Did it have anything with that evil air belief back then?
Hi, there's room for more information here, but while you're waiting, you may be interested in some earlier answers
/u/VetMichael in How effective were medieval or renaissance doctors, really?
u/reliable_information and /u/HeloisePommefume in How might the historic "beak nose" plague masks have been packed, and was there any empirical data regarding their effectiveness?