Hi---my dog exhibited the same symptoms. He is a 7 year old terrier and every year we battled some form of allergies where he would chew his hips/back side until it was raw. We gave the vet recommended meds every year. Then one year the congestion with troubles breathing at night it seemed, tiredness...we tried benedryl and it made him so dry. Then the vet said 10mg zyrtec at night. It was like a magic wand! I've since reduced it to 5 mg at night and watch for dry nose. He doesn't scratch himself raw, sneeze, cough, and he plays like a puppy now. I wish she had said that sooner..my mom's dog also had allergies to some unknown thing and was pink in the underbelly and she had tried everything. Zyrtec is on board and the expensive trips to the vet have decreased a lot! Cats can have it, too at 5 mg dose. My dog is about 50 pounds. Hope that helps. I'm not a vet and of course, you should run it by the vet first.