Summarize this article in one sentence.
CAD is a diagnosis of exclusion, meaning that other causes of itchiness must be ruled out before CAD can be diagnosed. CAD is the second most common canine skin problem behind FAD, so your veterinarian will probably want to rule out FAD first.  Treatments for FAD include medicated flea and tick shampoos, flea and tick sprays, and topical flea preventatives. Use the spray in a well-ventilated area.  Use these products according to the product label instructions, as well as your veterinarian’s instructions. You can also get rid of fleas by vacuuming your home more frequently and washing your dog’s bedding hot water. If your dog is still miserable and itchy after being treated for fleas, then FAD can be ruled out. Interestingly, fleas can trigger development of CAD. After ruling out FAD, your veterinarian will test for other skin parasites called mites: demodex, which causes demodectic mange, and Sarcoptic scabei, which causes sarcoptic mange (scabies). He or she will take a superficial skin scraping to check for mites under the microscope.  If your veterinarian does not see mites in the skin scraping, he or she will likely rule out mange. Even if no mites are present, the skin scraping may reveal bacteria or yeast, indicating a secondary skin infection caused by the scratching. Your veterinarian will treat your dog for these infections. Food allergies can make your dog feel itchy. After the external parasites have been ruled out, your veterinarian will want to rule out food allergies. Proteins are a common trigger for food allergies in dogs, so your veterinarian will recommend switching your dog to a hypoallergenic food that contains a protein he has not been eaten before (e.g., duck, kangaroo).  A food elimination trial involves feeding your dog only the new food for 8 to 12 weeks to see if his allergy symptoms go away, then re-challenging him with his old food to see if the symptoms come back.  If your dog’s itchiness persists throughout the food elimination trial, your veterinarian will likely rule out a food allergy. Hypoallergenic foods are available through your veterinarian.

Summary:
Treat your Golden Retriever for flea allergy dermatitis (FAD). Test your Golden Retriever for mange. Conduct a food elimination trial.