Old female dog that has been spayed.

Question
I saw an answer about the older dog that had been spayed that had
a swollen vulva. We had our female dog tested for estrogen and
there was none.  We have had her tested for everything and cannot
figure out what this is.  She chews on herself until she bleeds,
scoots around on her behind until it is red and more swollen. The
backs of her legs are swollen and red at the middle of the leg.
Any suggestions?  Thank you! The dog is 9 years old and is a wire fox terrier. Up to date on all vaccinations.

Answer
She could have cellulitis in the tissues back there from the chewing trauma. You need to have her checked for allergies as these sound like major allergic symptoms.

Redness, swelling, chewing, scooting around are all symptoms of a major allergy which can be flea related, food related or airborne allergens.

In all that testing that was done was she ever tested for allergies?

Without knowing what kind of tests she had run and not knowing what kind of food she eats, all I can suggest to you is to have her tested for multiple allergy issues and do a trail feeding period with a novel protein food to rule out food allergens or sensitivities.