The vast majority of itching is caused by allergy. I will start out by saying that allergic skin disease is a life-long condition that can be managed but not cured. It also requires patience and lots and lots of recheck appointments. There is no magic cure for skin diseases - she's going to need to be seen by a vet to tweak her treatment plan and keep her itch free every so often. Often in the beginning the allergy is steroid responsive (ie: gets better with steroid treatment) and they may only flare up once or twice a year, but they get worse as they get older, flaring up more often.
Allergies can cause dogs to lick their paws and scratch in many places on their body. They can also lead them to get secondary infections with bacteria and/or yeast. I suspect this is the case with Tia, since you are noting the scaling. Any secondary infections that may be going on, as these can make them much much more uncomfortable. This is often accomplished by topical treatments, oral antibiotics, and sometimes oral antifungals. It’s important to realize that it takes 3-4 weeks and maybe longer for bacterial and yeast infections to resolve with appropriate treatment. It’s very difficult to say what a dog is allergic to without a lot of testing.
There are three broad 'flavors' of allergy: flea allergy, food allergy and atopy (allergy to things in the environment like grasses, trees, or pollens).
With flea allergy, the itching and hair loss is centered on the caudal dorsum (the top of the lower part of the back), thighs, rear legs, and hind end. It's accompanied by the presence of at least one flea, usually many. Just one bite can cause an allergic pet to become intensely itchy and develop secondary infections that can perpetuate the itching even after the fleas are gone. Obviously flea allergy doesn't improve until the fleas are controlled. If you'd like more information about flea control, just ask and I'll be happy to provide it.
As for food allergy, pets can become allergic to a diet late in their lives just like we develop allergies as we age. In order to check for/treat for food allergy, we do what is called a 'food trial'. This is where the pet is fed nothing but a strict hypoallergenic diet. I use Iams Response KO, Royal Canin novel protein or Anallergenic diets in my practice however there are a lot of good diets out there. A pet must be on this strict food trial for 3 months to determine if it's really food allergy. I really recommend a food trial for dogs when I suspect allergy because if you get a good response from the hypoallergenic food, then you can give your pet less drugs in the long run. It’s important to be consistent and not give any treats that aren’t in the diet plan. Anything that goes into her mouth could cause an allergic reaction, so if she eats it and begins to itch it will mask any positive response you will see from the diet trial..
There are a number of treatments for atopy (or environmental allergy). Usually a food trial is performed first before these. A dermatologist can test the pet to find out exactly what they are allergic to and make an allergy vaccine, just like they do in people. This is called allergen-specific immunotherapy. Some pets can be managed with antihistamines (like benadryl) when all of their secondary infections have cleared up. Some veterinarians (myself included) have had a lot of success with a drug called Atopica. Atopica is a maintenance drug to help prevent allergy flare ups, however it can be very expensive. Another allergy maintenance medication that has great potential is Apoquel, but it is very new to the market and so far extremely difficult to come by.
If trips to the dermatologist and pricey drugs like Atopica aren't an option, many pets do respond positively to treatment with steroids. Steroids are potent anti-itch medicines but they do have long-term side effects. Steroids are great because they are very effective but if used too frequently can predispose your dog to developing life-threatening problems like diabetes. Typically I will use a course of steroids for a first time offender - in the hopes that it was a contact or seasonal allergen that will be out of the air by the time the steroids wear off. I encourage you to discuss the treatment plan with your vet. It’s also never wrong to seek a second opinion if you’re unhappy with your pet’s progress but be prepared that another vet may (or may not) recommend the same course of treatment.
Hope this helps! Please let me know if I can answer any other questions for you :)