Animals rub their faces on the ground to eat and really don't know better than to eat clean food and check for parasites.

Quit reducing everything to such simple shit, it's fucking retarded.

The drugs work via a specific function. That function can do many other things as well, we call these side effects and are reasons for off label use.

You shouldn't be looking at "omg anti parasitic!!!"

That's just being stupid.

You should be looking at HOW it works