Welcome to the PNW Sepp!
The blood results came back with several types of grasses, a couple weeds, and mold and dust mites. I started giving him the injections. I can't say when it officially worked, but after starting them he stopped having skin infections and the hives went away.
We started the series giving an injection every four days, slowly building up the amount we would give. So the first injection was 0.1ml, second injection 0.2ml. Sometimes dogs are so sensitive you have to give it in even smaller amounts than what is suggested. At one point I believe I gave 0.5ml or 0.6ml and he reacted to it - it stung when I gave it. Because he reacted to the larger amount we had to back off a little and slowly increase the dose. These days we're down to one injection a month, of 1ml of allergy serum. He takes the injections really well [thank god].
Not every dog responds super well to the injections, but if you can try it, I think it's worth it to do so. Heska says it's about 60-80% that respond. Steroids are the most common treatment for allergies. I've been on prednisone myself, and it made me feel horrible. I would rather hold off on using steroids for as long as we can. I definitely understand that this is an option and you need to do whatever you can to make your dog comfortable. But, if you can afford the blood work and shots I strongly recommend it because it has worked wonders for Sepp.
**Edited to add that there are also nasal drops now available. If injections aren't your thing the nasal drops would probably be fairly easy to administer.