My Yorkie Toy has all the same problems as you described for your Lexi. He weighs 9 pounds and is 11 years old. I tried everything as well. Nothing helped. I spent tons of money on useless products, medicines, prescription food, shampoos, pastes, sprays, you name it!
Atopica is very expensive. If you want to still give it to your dog after this, google it online and it shows you which websites have it the cheapest at the moment. Also try 1800petmeds, they have great coupons most of the time.
Atopica; no steroids, which is much better that pregnosone any day or the useless Benadryl. The Atopica pills are huge and liquid filled, so no pulverizing them and only when I put it in raw hamburger he would eat it, but sometimes he even refused then. It became a challenge to find different treats to hide that pill in. He vomited if I gave it to him to close to or after a feeding, so I waited 4 hours after his breakfast, gave him the pill and waited another 4 hours before feeding him again. That worked for the vomiting. It is true, the symptoms went away the very first day he took the pill, BUT the skin condition never ever got any better. He wasn't preoccupied with licking, scratching, chewing anymore, but his skin looked the same. Atopica will not cure your dog of his allergies, it will only make him stop feeling them!
I researched this subject to death and with all the dry kibble talk and home cooked vs. raw. I believe our dogs are allergic due to the food they ate all of their lifes, over vaccinations and a toxic environment. The cleaners, soaps, ect. we use in our homes. I stopped giving the Atopica because I felt that for a 2 dollar a day pill, it should've cured my dog, but like I said, it didn't. I'm trying something totally different now. Raw meaty bones and organs, no veggies, no supplements, no grains, no kibble of any brand, no canned cooked meat.
I'm giving this approach a one year try as I have experimented with EVERYTHING else for 10 years with no results but an empty wallet and a rich Vet and Commercial dog food business due to my ignorance of Canine nutrition and health. Bad, stinky breath and teeth, dry flaky skin, awful odor coat, red patches, black spots, oozing sores are not normal in dogs, so what are we doing that causes that???? Exactly! We are what we eat......
Sorry for the long post! I wish you good luck in your endeaver! PM me if you like for more info on Atopica as I fed it to my dog for a year and a half. He experienced no ill side effects from it, at least that!