It is most likly food allergy. Get her on a food without chicken, corn ,wheat or soy. When I ran my grooming shop we sold lots of nutro but now I sell more Diamond Naturals. I even feed it to my pets they have a nice lamb and rice formula. You can pick it up at Tractor Supply.
Once you change the food it will take about a month for the old food checmicals to clean out of system. Do a grdual switch over in 1/4 increments. 1/4 new to 3/4 old, 1/2 new 1/2 old then 3/4 new to 1/4 old. depending on her you can do this in 1 or two weeks.
IF you have her on a food like I listed then it might be flea allergies. Treat whole house and yard and get her on a spot on treatment. Tar and Sulfur shampoo is best to releif the itching.
Well, medicinally you can do benadryl and fish oil, they have a synergistic effect. My Snowball is 50 pounds and can have a max of two benadryl pills (get the generic kind they're cheaper and just as effective). I give her fish oil tabs 3 times a day and also drizzle about a tsp of flax seed oil on her food. It takes about 2 weeks for the results to be visible, but you'll notice that she stops itching almost immediately (gosh I love my vet .. she doesn't sell you unnecessary pills and other crap). If that doesn't work, you can ask your vet for prednisone (sp.), but there are some significant side effects which you should first discuss with your vet.
Raw honey is also one of those things that can help too ... there's no scientific evidence to prove it, but I've found it to be slighlty effective. Try and get it locally.
Also, make sure your pet is on a reliable flea preventative (Bio Spot On and Advantix work wonderfully) and to immediately get the fleas off you can use a CapStar ... and as stated above .. the food .. that's huge. Try a lamb and rice formulation from a good company (California Natural, Evo, Science Diet, Diamond is highly recommended by my sister in law, the vet, that's what she feeds her dogs ... Nutro...not Eukanuba, Ol' Roy, or any of those other companies). I personally have had good experiences with Nutro, California Natural, and Diamond. Evo is exceptional, but a lot of dogs can't handle it .. it's very very rich. Science Diet is nutritionally perfect, but unless a dog is raised on it, they probably won't eat it (I figure it's probably like us eating super healthy nutritionally perfect food). Corn is a common dog allergy, and if you're buying cheap food, it's probably one of the main ingredients. Def. follow the advice about gradual food change over .. otherwise you might have some stinky results .. plus if you have a big chested dog .. well we all know about bloat.
I am a dog groomer as well, and she is on eagle pack holistic select. good food. I have her on tereril P which is a low steroidal pill every other day. she gets 1200 mgs of fish oil twice daily, and I have had her tested twice.
I just want to give her some relief during her weekly baths as to where she will not start stinking so fast. i use soothe clorhexiderm shampoo now.
I would be concerned with drying your dogs skin out with hand made soaps, especially if you end up using it frequently. On that note, I did make soap for my dogs (but mostly use Tropiclean no soap type shampoo for them now). It was mostly olive oil (with coconut, palm, etc). I use essential oils and not fragrance oils. I also used a diluted ACV (Apple Cider Vinegar) rinse after washing all the soap out.
I only use hand made soaps for myself and I use an ACV rinse several times a week. It makes my skin feel nice.
My dog used to get red, itchy and smelly ears that would drive him nuts. The vet said to change his food so we bought an expensive natural high protein food and that worked for awhile. Then one day his ears got really thick and heavy and he quit eating all together.
I took him to a different vet and he said to feed him something bland like cooked oatmeal or rice for a few days and then introduce a new food item every couple of days to see if he could handle it.
Turns out he was allergic to corn. I now make his food myself. Kind of an effort since he's a big doberman cross but he's worth it. A ground meat blend (usually beef or some moose a lovely neighbor donates) with rice, oatmeal, water, canned tomatoes, carrot peels, spinich, apple peelings and seedless cores, sometimes cranberries and yams, and beets. Anyway, he loves it and everyone who sees him comments on how healthy he looks and how shiney his coat is.
His ears never bother him anymore and he's been on this diet for a year now. He also hardly ever drinks water. I guess he gets enough in his food since its wet. Biscuits make them quite thirsty.