Last year we started our 3 year old yellow Lab, Annie, on Atopica. After several weeks, her scratching lessened significantly, her beautiful coat returned and she was much more herself. It was wonderful. Then, at some point I noticed that about 1 or 2 hours after we gave her the Atopica, she would start scratching compulsively, just as you described. This would go on for several hours, and sometimes through the night. We stopped the Atopica after a few months to try other remedies, including homeopathic medicines and bio feedback, which helped but nothing stopped the scratching. We started her on Atopica again this week. I always wondered about the increased scratching after taking Atopica. I searched everywhere for possible explanations or for others who experienced this but never found anything until I read your post.