There is an amino-acid called Serene or L-Serene that most mammals have in their skin. I have heard that this amino-acid concentrates in the hands, feet & paws, especially in males. Serene is said to cause fish to spook so washing your hands should be a good idea. Maybe salmonids have been naturally selecting wariness towards Serene from migrating past predators like bears standing in the rivers.

Beezer