My 1.5 yr old Shepherd mix has skin irritation and has been itching constantly. I purchased Nuvet Plus hoping this would cure the itchiness. I also changed his dog food to Canidae Pure grain free high quality food made with duck (since I read that duck is not listed as one of the top foods that dogs are allergic to). I gave recommended double dosage of Nuvet Plus for four weeks and did not see any difference in his skin or coat. I know it's recommended to try for 6 weeks but there was no marked improvement at 4 weeks. We ended up bringing him to the vet to get him checked out.