I visited Pershore Abbey today. Again, I started getting really bad hayfever. No doubt most of the pollen in the building was brought in on visitors shoes.
Gojirah was absolutely right that it makes a difference.
This blog recommends that you adopt a shoes-off policy in your home, not just for family but also for guests and other visitors. Socks, slippers and bare feet are fine indoors, but not shoes. Just say NO to shoes in your house!