Allergy that has caused skin infection

Question
We have a Doberman who has been suffering from allergies over the past 6 mos.  We know he is allergic to weeds, and similiar which in the past he gets an inflamed nose or eyes - nothing Benedryl doesn't fix.  Over the mos he has developed a skin irritation - they appear to be like blood blisters in the shape of large pimples all over his back - not so much his undercarriage.  He is extremely itchy and uncomfortable - of course he's had ear infections too (these have healed).  Currently we've been instructed to feed him Hills Prescription Dient z/d ultra Allergen  Free food.  For the most part it is working - except his coat is very coarse and appears to be thinning. We've been given a Fatty Oil solution to add to his food to correct this. This food is extremely expensive and only last (if lucky) 2 weeks.  Do we have any alternatives?  As in humans is there not an anti-histimane he can be given?  What are the causes of this skin infection - he's been on the same food since he became part of our family 2 yrs ago and suddenly this?  We would like to find a solution without having to be on prescription dog food for life.  Thank you for you time

Answer
z/d is a good food for helping diagnose food allergies.  The dog should be on it for 2-3 months without any other source of protein being given to see if it is the food causing the skin problems or not.   No treats, rawhides or even flavored heartworm medicine can be given.  One word of caution...they should not be on a fatty acid supplement while on z/d because the fatty acids have fish protein in them, which will interfere with the food trial.

After the 3 months, if the dog is doing well, then individual protein diets are given to see if the skin reacts to that protein.  For example, a chicken only protein food is added.  If the dog does well, then he is not allergic to chicken and a chicken based food can be fed.  But if a beef protein diet is given and the skin breaks out again, then the dog is allergic to beef.

IF there is a skin infection, then antibiotics need to be given for several weeks util the infection is under control.  In Dobies, some of them have a genetic problem that makes them more susceptible to Staph pyoderma (Dobie Bumps)and those dogs need antibiotics long term, often given on the weekends only to control this. Many other types of disease can cause Staph pyoderma, like low thyroid hormones and external parasites.

If the food trial is not successful, then rather than using an antihistamine, the dog may benefit from some steroid therapy to decrease skin inflammation. Ask your vet about a short course of steroids to see if that helps.

Allergy testing and desensitization can also be done, but this may take a year to show results and it is expensive.