Not sure how safe they are but they make repelent in wipes now for kids. If they are safe for children it should be safe for dogs. Maybe at least carefully wipe areas where they can't lick, on their chin, very carefully a small wipe in the middle of their eys & the top of their head.

Just wipe off w/ normal baby wipes afterwards. If they do get to licking eachother just keep them occupied with soemthing else, like food or toys etc..