Dog Allergies Treatment

My dog was rescued about three months ago and we don’t know anything about his history. He has allergies but we are not sure if they are environmental only, food only, or a combination of both. He does not have any fleas.
Last week I brought him to a new vet (the old one was useless and a firm believer in feeding Purina or Iams) and he decided on a mild course of action as a first step. He prescribed 1 adult benadryl (25 mg) twice a day, Welactin fish oil once a day, and Douxo Calm shampoo and spray. He told me to keep feeding California Natural lamb meal and rice for 3 months, which he was already eating for the past 3 or 4 weeks, but with treats that had other ingredients.
The shampoo treatments call for 3 baths in 7 days, and then to use the spray every 3 days for a month. After the first bath the dog seemed to be better, with a soft coat and calmer skin instead of the pink/red skin he always had before. But yesterday I began to notice he has some raised spots (they look like scabs) in his back which seem worse today and he has some tiny red spots that look a little scaly in the belly area. He is extremely itchy this morning, even biting and chewing his back.
During the exam, the vet noticed one spot that looked like a scab, but today there are at least 5 more of those, so I assume it is getting worse even though he is on Benadryl, the shampoo, etc. I was wondering whether anyone here has seen those symptoms before and could help me to suggest something else to my vet. I cannot believe he would miss something as serious as mange, for example, but maybe there is something else he is missing. We discussed the blood test for allergies, but he said that most of the time they are not helpful because they cannot diagnose food allergies and often it is impossible to keep the dog from getting in contact with whatever it is he is allergic to in the environment. Even so, I am considering it. What is the price range?
I also had tried to get the dog to start eating EVO red meat yesterday by introducing it as treats, which he would not eat. I managed to get him to eat 2 pieces a little after 12 pm yesterday. Could an allergy to beef or another ingredient in the food cause such a powerful reaction this quickly after such a small exposure?
Thank you and I’m sorry this is so long…

This entry was posted on Wednesday, February 10th, 2010 at 2:50 pm and is filed under Flea Allergies In Dogs. You can follow any responses to this entry through the RSS 2.0 feed.