Hi,
As I mentioned in another post, our new rescue cocker Tia was very itchy. Apparently she has thickened skin around her vagina, and the vet put this down to an allergy. I now have to rub in cream 3 times a day, and so far not so itchy.
She also said that as allergy testing is so expensive, and as there may not be a definitive result, then it wouldn't be done.
Not much help to you I'm afraid!