Hello all, my lovely 1yr old pup has had a rash on and off for the majority of her life... started around 12 weeks with a small rash that didn't really irritate her and it came and went again and again but is now back with a vengeance. She has hardly ever been rash free and this time it is so so sore and none of the medicine given by vets is even touching it.
Does anyone have a clue what it might be? She's had skin scrapes to check for mites, etc. Allergy tests, all negative. The vets have no idea and each time I take her I end up having to put her on anti biotics and/or steroids. It's really sore for her now and I'm fed up on her behalf!! I have tried taking her to different vet practises in the hope someone would recognise it, but no. 
Photos attached:
First photo is 10 days ago, last photo is now. After a course of steroids + antibiotics