I think the person with the sensitivity is where the responsibility lies. I have a cat, and he *is* free to roam. However, he doesn't jump up in the fabric closet, "spray", claw, or otherwise defame my work.
I don't smoke, but I can see where people that do wouldn't advertise the fact that they do. Because I've received some VERY smelly, brand spanking new fabric that smells like a bar when I open it. For me, it's a difference between having to wash it right away versus tucking into my stash asap, like I would if I purchased from a store.
There's no way to know which buyer will be sensitive to what environmental allergen. There's a difference between being sensitive and just annoyed. And, if they're severely allergic, they have been that way for a period of time and know to advocate for themselves and what they introduce into their environment.