I've been using Benadryl on dd's. Lacto-calamine is good as well. Calamine is too drying, and will make them itch even more when it dries out.
Oatmeal baths are helping too; stick some oatmeal (porridge oats are fine!) into the toe of a pair of tights or a stocking, tie it up and squidge it about in the bath. Very soothing. Or put some bicarb into the bath if you haven't got any oats.