Thanks for your question, my name isXXXXX and hopefully I can be of some assistance.
I'm sorry to hear that your dog is not feeling well, but hopefully there is an underlying condition that can be treated medically.
Based on your description it is likely that your dog is experiencing skin allergies, or canine atopic dermatitis (atopy). This is likely a genetic predisposition of the body to react in a hypersensitive way to substances that would usually be considered harmless, such as grass/tree/weed pollens, house dust mites, flea bites, ect. The immune system reacts abnormally when exposed to these substances in cats/dogs with underlying skin allergies, which causes a mass of histamine and other inflammatory mediators to be released in the skin. This causes a great degree of inflammation and itch (pruritis) in the skin, which dogs and cats react to be licking/grooming excessively and scratching. This can then commonly lead to abrasions and/or infection of the skin. Golden Retrievers are a classic breed to be affected with skin allergies. Bacterial infection of the skin usually demonstrates a telltale lesion that is round to oval, red (erythematous), with a darker center, and commonly with an overlying yellow flaky crust. This type of infection in the skin can also commonly lead to hair loss (alopecia) at the affected sites.
Based on your description, it sounds like your dog has not responded well to medical treatment with antibiotics. This is unfortunate, since most dogs with this type of presentation respond very well to a 3-4 week course of antibiotics, and a course of antihistamines or a short tapering course of prednisone for itch relief. That being said, many dogs require some form of longterm treatment to control their skin allergies. Only about 10-20% of dogs with skin allergies can have them controlled by an anti-histamine alone, which is a class of drug that I commonly use to treat my skin allergy patients with longterm, as they are relatively safe to give on a longterm basis. When dogs have a flare up of itch and skin infection, they are usually in need of longterm (3-6 weeks) treatment with antibiotics, and likely glucocorticoids (prednisone) to quiet some of the skin inflammation/infection for probably 2-3 weeks.
That being said, treating longterm with glucocorticoids should be avoided if possible, and there are safer alternatives for the treatment of skin allergies longterm, most notably allergy vaccines and a drug called cyclosporine. Until your dog is on some kind of longterm management for his allergies, the itching and skin infection are likely to keep recurring. Since it seems your dog might be responsive to anti-histamines, I would attempt longterm treatment with one of these types of drugs during the times of the year that the itching and skin infection occur. For most dogs on the east coast this is bi-seasonally during the spring and fall. Anti-histamines are generally very safe drugs to use longterm, and I have many patients that take them three times daily for the length of the summer (7-8 months out of the year) If you would not like to attempt treatment with the oral anti-histamines, I would talk to your veterinarian about getting your dog tested for skin allergies and initiating allergy vaccines. Just remember that there is no "cure" for skin allergies so it is a disease that is managed as best as possible and will certainly be a lifelong problem for your dog.
Additionally, atopy is a diagnosis that is made by ruling out the other common causes of skin infection and hair loss in dogs and cats. For cats/dog that present to my clinic for the first time with this type of skin disease or presentation, I certainly perform a formal workup to rule out any other causes of itchy skin. This would include a check for fleas, other external parasites with skin scrapes, and a fungal culture to screen for ringworm. I sometimes also place them on a hypoallergenic diet for 8 weeks to rule out for food allergies. In your dogs case, a skin culture to rule out a resistant bacterial skin infection may prove helpful since previous courses of antibiotics have not been effective. The other alternative would be a longer course of antibiotic with an effective drug.
As I stated previously, an antihistamine alone can probably help about 10-20% of dogs with underlying atopy as the cause of their skin infection/itch. This usually doesn't "cure" their allergies, but rather lessens the inflammation and/or makes them not want to itch their skin as much. If you see a decrease in the amount of skin lesions while your dog is on an antihistamine, then it is likely working and you can probably continue to give the medication through the itchy season, or year round if that is the case. I commonly use Diphenhydramine (Benedryl) in my canine patients at a dose of 1mg per lb. of body weight (a 25 lb. dog would get 25mg by mouth two-three times daily).
I hope this answer was helpful, I wish you and your dog the best. The other option to consider is to ask your veterinarian for a referral to a dermatologist. I commonly send my skin cases that prove difficult to manage to a dermatologist that has more time and experience to treat the more complicated cases. I'm sure your veterinarian would be happy to set you up with a veterinary dermatologist in your area.
I wish you and your dog the best.
Positive feedback is much appreciated.
Edited by Dr. Rick DVM on 10/30/2009 at 11:38 AM EST