I used to work at a pet shop and am allergic to mites. My boss would always make sure I was scheduled for animal delivery day so I could handle the new animals and immediately tell if they had mites or not and needed to be sent back. Customers heard about this too and started bringing in their pets to see if they needed topical treatment for mites. The vet across the street started sending suspected mite cases to me first because it was quicker and more accurate than checking the animal manually. Local small animal rescue heard from the vet so they started using my services too.
Luckily it was just itchy and hives and they went away quickly so I didn’t mind too much. It was a cool party trick. There was also a brand of bedding (Carefresh) that was frequently shipped to us infested with mites (probably had rats or mice at the warehouse) and that was pretty annoying because they didn’t believe us and wouldn’t take product back.