Personally I like it because you never know if a guest has a food allergy or flower allergy. 

If your restaurant is Billy Bob's Crab Shack you don't want a bunch of people with Seafood allergies showing up.

I'm not allergic, but consider the health ramifications of the gym client with pet allergies who is running on the treadmill (already short of breath) and sustains an allergic reaction from the pet.  

I already have serviceable flooring, but some of it is carpet and I have allergies that are much improved when the carpet goes away.

And there are many people with cat allergies so it can sometimes come up in re-renting a place.

She sent a follow up email complaining about the following, to name a few:Small scratch on stainless steel fridgeslight discoloration in grout about sinkpenny size chip in tubscreen doors don't slide smoothlyAdditionally, she asked us to come spray the house because she saw centipedes and has a bug allergy.

if their ESAs are bogus, it may be enough to get them to look elsewhere.  2) require them to have renters insurance that lists each animal as covered.  3) This one may be difficult/impossible if you were already allowing pets, but inform them that they will be charged for placing the unit back into an animal free state including professional HVAC cleaning (potential tenants have allergies so there is a need for animal free properties). 

I try to keep several homes pet allergy free.I've had a person rent furnished and asked me to store one bed (to bring in their kids furniture) then the other bed (for their father to move in with his own mattress) and then ask me for a discount because they aren't using all my furniture...lol.

I always price my pet deposit separately and make it nonrefundable because my cleaners have to do a deep clean after each pet in case of allergies. 

Personally, I have a flood allergy.