L.V.
not sure about the siberians, the allergies are usually due to the dander and the undercoats of the cats. I do know that devon rex and cornish rex cats have no undercoats, and very little dander. I have a friend who got a devon, and she hasn't had any problems with her allergies. They are very affectionate cats, and lots of fun. They are a lot smaller than a siberian. Usually, you want to stay away from a long haired cat if you have allergies. You might find a breeder and talk to them about the siberians, they would be your best source of info.
Just as a side note, in reference to another response-- if you get a solid white cat, have its hearing checked. If the cat is all white with blue eyes, it is more likely to be deaf. If it has one blue eye, it is probably deaf in the ear closest to the blue eye. There are occasions where a blue eyed white cat has complete hearing, but that is not the norm. Just be aware of it, and be able to understand--also, just because it may be deaf, does not mean that it can't be a great pet!!
Good luck!