Poor Ranger, she must be miserable! I encourage to get a copy of this month’s Whole Dog Journal… and start keeping notes. When is she most itchy, what does she eat, what’s the daily pollen count, etc. The more information you have, the better you will be able to sort out the cause.
As much as I like raw , I’m not a big fan of Nature’s Variety. It’s expensive and they add a multi-vitamin supplement, which is typically synthetic stuff from China. One of the less expensive and “simple” pre-made raw foods is Oma’s Pride (my husband has recently become a distributor for them). However, because of what’s going on I’m going to suggest a more “square one” approach first.
Ranger needs you “clean up” her world as much as possible. I would thoroughly clean the house (vacuum, damp mop with just water, wash all dog bedding and extra rinse, etc.). Change your furnace filters and keep doors and windows closed for the week. Wash both dogs. She is to have no flea or heart worm meds, no commercial treats, no processed foods.
Fast Ranger for 24-48 hours (but give lots of water), then give her very simple raw meals for one week… one protein and one starchy veg, like chicken and sweet potato (if you can, I would opt for organic meat for this test, bony pieces are fine). No supplements or fish oil (while generally good, some dogs are itchy with fish oil and the balance of fatty acids matters). Just as basic as can possibly be for a full week.
Your goal is to get her itching under control by removing as many potential allergens as possible. I would also give her 3 doses of the homeopathic remedy, Nux Vomica 30c, 12 hours apart. This helps clear toxins out of the body. If you succeed in getting her feeling better by week’s end, then we can discuss where to go from there.