The question struck my mind as I read this part from a wikipedia page:

Sigurd strapped the head to his saddle as a trophy, but as Sigurd rode, Máel Brigte's buck-tooth scratched his leg. The leg became inflamed and infected, and as a result Sigurd died

Source: https://en.wikipedia.org/wiki/Sigurd_Eysteinsson#Sigurd's_Howe

If you have answers not relevant to Europe or the time period designated, I'd also be interested in hearing those as long as they're before modern medicine began gaining traction.