Sedation is the main side effect, but for my Golden, it didn't really do much of anything (sedation of anti-itch). Its worth trying however. If it doesn't help, you might ask your vet for amytryptiline (a tricyclic antidepressant that has strong anti-histamine properties). You might have trouble with getting a small enough dose, and it also is sedating (which acutally helps, at least they don't scratch as much).

Good luck!

Jake's mom