I usually allow only one of my dogs - my mountain feist - as she is quite small and very "cat-like" when she's not being her usual hyperactive self. Mountain feists boast short fur, so fur and dander are not an issue, either. The only time that she's not allowed on the sofa or bed is after she's come from outside.
My other dog is not allowed on the sofa, not only because he's quite large but also because he sheds A LOT (he's a husky-chow chow mix, so it's only natural). However, he is allowed on the bed. Shedding is less of a concern there, as the bed spreading seems to resist fur and dander sticking to it; any miniscule amounts of such can easily be removed with a lint brush...
My other dog is not allowed on the sofa, not only because he's quite large but also because he sheds A LOT (he's a husky-chow chow mix, so it's only natural). However, he is allowed on the bed. Shedding is less of a concern there, as the bed spreading seems to resist fur and dander sticking to it; any miniscule amounts of such can easily be removed with a lint brush...