If you're going to give an oil supplement, fish oil (or salmon oil) may work better than flaxseed. From what I've read, some dogs have a hard time processing the flaxseed oil, as it's derived from plant matter, so they don't get as much out of it. Also, most dogs' diets already contain enough omega 6, it's the omega 3 levels that are low, and a fish oil will balance that out better than flaxseed, which has both omega 6 and 3.
For most dogs, I think maintenance dose of the fish oil is 1000mg per 25 lbs or so, but a higher dose may be more benefitial to dogs with joint problems, skin problems, etc, up to 1000mg per 10 lbs body weight.
Also, a note on steroids, they can be nasty catalysts if your dog is already predisposed to certain disorders. When our younger APBT was with her former owner, she had a cortisone shot for some swelling and fluid buildup around the stub where her leg was amputated, and about a month later, was diagnosed with diabetes. I later read in several trustworthy sources that the reason for the peeing, excessive drinking, and eating some dogs show when they're on steroids is because it puts them in a temporary diabetic state (don't remember exactly how now, but I believe it inhibits the insulin's effectiveness at breaking down sugars), and a few dogs remain in that state permanently. It's pretty uncommon for a dog to develop diabetes so young (14 mos old), so it would make sense that something may have set it off, though she may have also been genetically predisposed to having the disease. Granted, we really don't know if there was a connection, and even if there was, it isn't a very common occurence, but worth considering if your vet is one to go straight for the steroids in cases of allergic reactions and inflammation, especially if you don't know much about your dog's family history.