What a great question! I had to think hard to come up with something. Smoking would be the #1 "not allowed", but that pertains to my whole house and car. Maybe anyone or thing with dirty, smelly hands or paws.
My cats visit when I'm in the sewing room but rarely when I'm not. They like to watch me sew. They never bother anything. Hardwood floors so anything dropped is easily seen and picked up. TV is usually on Youtube so I can watch/hear quilt videos, like MSQC.
I do eat in my sewing room occasionally. More in the winter because it's upstairs and warmer. But I never have my quilting/sewing project near the food. And I will sometimes keep some Vitamin "C" (chocolate!) nearby, cuz ya know we quilters have to keep up our strength for those marathon quilting sessions.