Hello, Customer and welcome back to Just Answer.
I'm so sorry to hear that Sammie has been experiencing these uncomfortable symptoms for about 3 years, now.
From your description, it does sound like an allergy to something, and as I'm sure you know the list is quite lengthy. She could be sensitive to the laundry detergent and/or fabric softener you use, if she sleeps on your bed and/or you wash linen (towels, blankets, etc.) for her bed in the same brand. She could be allergic to any cleansers or carpet shampoos/powders you may use; scented candles, plug in air fresheners, cigarette smoke if anyone smokes in the house, etc., things along that line. Here is more information about allergies in cats: Allergies
Changing her to a grain free diet was great, but some cats are allergic to the protein source (meat) in their food and need a limited ingredient diet (LID) containing protein and carb alternatives. Royal Canin, Natural Balance and other manufacturers make these types of foods and they are usually available from your vet if they are not carried in your pet supply store.
After all these years and your vet trying to resolve the problem to no avail, it might be a good next step to have Sammie evaluated by a veterinary dermatologist who will have the experience and equipment to hopefully, get to the bottom of this problem and then prescribe the most effective treatment. Taking a skin scraping (painless) from this general area for culture and analysis under a microscope would be helpful, as would checking her for ear mites which could be falling out of her ears onto the fur near her eyes/nose and causing this intense itching. Ear Mites
Other external parasites like fleas (you don't necessarily have to see them) could also be a possibility. Indoor only cats can get fleas brought inside by humans on shoes and pantlegs.
Keep her claws trimmed on a steady basis, so she does less damage with them when she scratches, and bathing the area with a warm dampened cotton ball, then gently patting dry, should help. I would recommend 'soft paws', which are vinyl nail caps put on the claws with a special adhesive, but they are usually difficult to get on and need to be replaced about every 6 weeks. They are inexpensive and sold in all major pet supply stores, so if you want to give them a try, they might cause Sammie to do less damage when she scratches in this sensitive area.
Discuss with your vet if she should be given antihistamines or steroids now, to decrease the itching, just until you can get her seen by a veterinary dermatology specialist. Specialists are usually found in ER vet centers and Veterinary Colleges. You usually need a referral, which you can get from your regular vet.
I hope all will be well with Sammie and the cause of the itching is diagnosed and treated, so she's feeling much more comfortable!
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