Skin issues can be so hard to deal with and this does seem to be an allergy. It could be food, something she is in contact with or inhaling. I would try to stay on a fish formula and feed her nothing else, no Greenies, treats, etc. What is her bedding made out of? You might try adding some Omega 3 daily.
My daughter is fostering a dog with allergies and nine of the above worked. Finally took her to a Specialist who did skin testing. Highest allergic was dust mites, which are everywhere! She is now getting shots every other day to try to desensitize her, just like they do with people with allergies. You might need to get some testing done to try to determine the cause.
I'm wondering about the "fresheners" are they all contained in air fresheners of some sort OR are any of them shaken or sprayed? Powders & aerosols can definitely affect an allergic human, dog, cat...
Also, carpets, if cleaned can be extremely irritating to pets & humans alike if they have allergies or sensitivities. I you shampoo your carpets, use ones safe/safer for allergies. If you have recently shampooed or sprayed anything on your carpets or furniture... shampoo again using allergy safe &/or several plain water rinses should help.
The other reasons can be, food allergies, (frequently grain in food) is very common yet not acknowledged allergy.
Jenny, died at age 17 but spent her whole life with irritated skin, the only things for her that worked were baths in Head & Shoulders (it's medicated for skin) & yes, adding Omega 3 to the diet, Salmon was her skin relief treat.. So she got it regular.
Deb on the other hand is stubborn & sneaky & only does good as long as we babysit her outings outside so she doesn't sneak near the chicken grains & poops out back.
Salmon for her too works great, but now that we're no longer in Alaska, it's harder to afford. However, we do us the Head & Shoulders baths for her too to provide her with added relief.
All our other dogs rarely had these issues. Makes me wonder if this rise in grain allergies might not be more from some treatment used on grains more today than previously. (That's just a personal pondering...)
And of course, hydration, water is essential to skin.
I would definitely can the air fresheners. I don't think breathing perfume constantly is good for anyone.
As for the skin, I have always used probiotics in my dogs for many reasons. They certainly have no side affects, and could help. I never had any gauge on the amount, but I would give my 50 pounder 25 billion to 50 billion bacteria count a day if there was an issue, and much lower maintenance doses off and on. Sounds like a lot, but it really isn't. Me and my wife use it regularly on a maintenance basis.
There are topical things you could also try, bathing with oatmeal, perhaps a boric acid/ water mixture (research the ratio) in case it is a skin bacteria. You could also try applying aloe.
If it is what they call 'hot spots', Adams makes a topical over the counter medicine. I'm pretty sure Wal Mart sells it in the pet supplies. I think it contains sulfamethoxazole.