i own a yorkie that has allergies! my vet had me feed him a hypoallergenic food(medi*cal) and bathe him in an oatmeal shampoo! she also told me to get rid of any plastic bowls too! the thing is he still scratches. i got fed up with him suffering so i dished out $270 to get the allergy tests done!to be honest...i'm glad i did because in no way would i have found out all his allergies by elimination! he has a total of 32 with 7 of those food based!(chicken,turkey.oatmeal,peas,carrots,kelp,an d brewers yeast!) so as you can see the oatmeal shampoo made it worse for me and the food also had oatmeal in it!i am having a VERY difficult time finding a food for him with these allergies!i have an appiontment with my vet again next week to discuss it! your dog may have more allergies besides the food ones!my yorkie is also allergic to house dust mites!if you can afford it i would go and get the allergy test done so you know what you are dealing with! sorry to say this...(but i i can relate to what you are going through) i feel that my yorkie will never be itch free or have completely healthy skin!
i do find though that hydrocortizone cream helps with the itching! that's about the only tip i can give you from my experience that works! sorry that i can't be much help! i hope you find out what allergies your pooch has(and that it's only one or a few...not 32!lol!) so you can deal with it head on!good luck!