my 7 year old black lab has...

Question
my 7 year old black lab has lost all the hair around his butt area and it
is red and oozy all around the area and has now spread to his genital area
i have had him to my local vet who treats him with antibiotics prednisone
and an injection of something which clears it up for a few months but then
it returns the vet isnt even sure what it is any help you can give me
would be appreciated  

Answer
I can not diagnose the problem over the internet without seeing the lesions.  I would be concerned about fistulas.  I would recommend culturing the oozy areas and also getting some biopsies of the lesions.  This may be due to an auto-immune condition or underlying allergies.  He may benefit from Cyclosporin therapy.  Definitely try to switch the diet to an all natural Fish and Potato diet made by Verus or Wellness as that is likely to help the skin.  Also, start supplement with Ester C 500 mg three times a day and add PROZYME into each meal.  Good luck.