However the wife reports that she is "allergic" to the bathtub and both her and their youngest daughter's skin breaks out when they take a bath.

and second, It's so expensive, and you've just put it down, you can't afford to replace it, so you CAN'T even consider it IS that causing your sudden watery eyes, burning sensations in the eyes, nose and throat, nausea, coughing, chest tightness, wheezing, skin rashes, and allergic reactions.

If they've somehow gotten allergic to your account or your IP address and don't want you to post for awhile I would be willing to post some ads for you from my craigslist account - you could just send me some copy pics, and contact info.

Almost like an allergic reaction.

At one point I had to do all adjoining units,, 4 total,,, was a nightmare,, had to pay one tenants doctor bill for allergic reaction she had to the bites.. she had just moved in,, guy next to her had them.. 

Do not want to get sued by other Tenants who claim to be allergic and courts tend to rule against landlords should I refuse to rent to them?

They also can harbor mold and some people might be allergic to them.  

Many people are allergic to pets, cats specifically "even if" the carpets etc were cleaned.  

Imagine my new tenants are allergic to cats and this cat sneaks into the house ?

Allergic to bullets - that's why.