Ah, yes, this is very true as many GTers will agree, when a favorite food of many changed the "source" of some ingredients. The formula was exactly the same, but when the source changed, it wreaked all sorts of havoc with many, many dogs! Having an itchy dog myself, it's very tempting to try everything at one time in an attempt to give them some relief! A muzzle with a stool cup may be a temporary fix for keeping Arrisa from chewing/biting herself raw - if only when you are away from home.
Sure hope you get some answers! Hope Arrisa feel better soon!