Consider flea allergy dermatitis, if you have not already ruled it out. Dogs that are allergic to fleas can be totally miserable if they get even one flea bite. If they happen to get several flea bites at the same time, they can react like your dog.
Also, the fact that the problem started up after she was spayed makes me wonder if there is some kind of hormonal issue. I don't know where to go with that, but I would get curious about it and explore it. I know there is a female hormone substitute that is sometimes given to older spayed females that have urinary incontinence. I might ask the vet about trying that, just to see what happens. Just a thought. If you're desperate, what the heck?
Good luck.
It might be helpful to consult a homeopathic/holistic vet. Try and see if there is one in your area.
remember to, be careful with your pets as you would your self, ALL Meds Have Side-effects. sometimes with sensitive people certain meds can make things Worse Rather then better. heres a place to thumb through things?
http://fallbrookvet.com/html/home.htm
if your dog, has dry mouth, brush their teeth after they eat also, Im sure it does the same thing to them its done to me, only no one warned me, Cavities Bad even tho I took immaculate care of my teeth b4...
Youve got your work cut out for you, odd tho, that your dog had no issues until she was fixed... look into what ever meds were used on her from and at the vet, and see if they list side-effects.
There is a med called Atopica.I use it for my bulldog we have tried everythig for him as well.The Atopica has really worked well for him,Before he was on steroids benadryl,and others.When he started taking it within a few weeks he was fine.Now he can go out and play and we dont have to worry about all the skin issues.If he does look a little raw then we do the sterioids with it for a couple of days and then he is fine again.We have only had to use the steroids very little since he has been on the Atopica.Call and talk to your vet about it and see how he feels about it.Good luck i hope she gets to feeling better soon.Please keep us posted.