Itchey dog needs help!

Question
Hello, I have an 8 year old 30 pound mixed breed (terrier type) female dog.  She has a severe itching/scratching problem.  We have gone through the basic regimen of creams, then shots, and now she is on Atopica.  The Atopica works fairly well, as the creams and shots didn't work at all, but it hasn't worked great.  She has to take the 100mg size pill, as the 50mg doesn't help much.  This is obviously a very expensive pill, and like I mentioned, it works good, not great.  It doesn't seem to be doing the job that box of $100+ pills should do.  My question is if it could be something in our house, such as allergies in the air, dust, etc. We moved into a brand new house in a different town about 2 years ago.  The itching started about 6 months after we moved in.  She will lick and lick until her paws and stomach are raw and red.  We probably don't vaccuum the house as much as we should (once a week) and we don't have an air purifier.  Is it possible that this could be our problem?  Can you recommend a good air purifier for pets?  Or should the 100mg Atopica knock out any allergy problems, and it is something else?  Is there a simple household test to see what it could be?  Thank you for your help.
Todd Hartz  

Answer
I am not sure about what household testing kits are out there but mold is a very common allergen as well as dust mites and storage mites.  

Certainly an air purifier won't hurt and may help.  I have hamilton beach air purifiers in my house to help with my allergies...I do not have a recommendation as far as what is the best brand.  Certainly you should vacuum more frequently and avoid carpet fresheners as well as scented sprays, candles and airfresheners.

I would highly recommend a fish-based diet to help her skin (Wellness, Verus and Flint River Ranch are all great all-natural brands) and eliminate the compounding effect of food allergies, which a very good possibility since she only has a partial response to the Atopica and is licking the underside.  I would also be concerned about secondary yeast skin infection from all the licking and recommend a low dose of ketoconazole which can also increase the effectiveness of the Atopica.  Atopica is expensive, I know, our one beagle has bad allergies but it has much less side effects than chronic steroid use.