Yes, you can use Tavist (you can literally use almost ANY anthistamine on a dog). You MUST have the right dose for it.
I've pm'd Janet, Oh Queen of Links. I know she's got a link for doses for anthistamines and I Just plain could NOT find my Pill Book Guide to Medication for Your Dog and Cat last night Jaime.
Folks, Jaime is a really nice lady I've known for a while. She has an itchy dog -- she oughta fit right in with lots of us here. I just couldn't lay my hands on that book last night and I knew someone here would have it.
Tavist is ....clemastine. Jaime - just watch the dose because it's available in more than one strength over the counter I *think*.