I am sorry to hear Gordie suffers so from allergies. My name is Rebecca. I am a veterinarian and will do my best to help.
What treatment did you try? I don't want to suggest something you already tried, and there are so many.
Bear in mind, there is no cure for allergies yet. We can only try to control the scratching, and the secondary infections that are caused by the scratching.
When a dog's skin turns black and waxy, that is usually due to a yeast skin infection causing by the itch/allergy. I treat that with shampoo containing ketoconazole (not available over the counter) and sometime oral medication like fluconazole. You can try applying topical over the counter ointments to these areas like Lamasil or Miconazole ointment.
The main thing is to control the scratching. Every dog is different; no one medication works for all dogs. You can try over the counter anihistamines like Benadryl or Claritin, steroids like prednisone, or the new drug Apoquel. Apoquel is by prescription and about 80% of itchy dogs respond to it, stop scratching, without the side effects of steroids like prednisone.
If none of these work then immunontherapy, weekly shots to desensitize him to the things he is allergic to might help. To do immunotherapy, you have to do testing to determine the exact things he is allergic to, and have serum made up for those allergens.
These supplements have all helped some dogs: probiotics, quercetin, nettles, evening primrose oil, fish oil, anti oxidants.
Allergies are complex and difficult, and there is rarely a simple easy solution. This new drug Apoquel is the closest thing yet to an easy solution, but it does not work for all dogs.
Let me know what else I can help with or answer. Rebecca