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It's possible your dog has or had sarcoptic mange and Revolution is an appropriate treatment. If the dog is over the mange then you are probably dealing with secondary skin infections, and may need an antibiotic such as Cephalexin. If I were you, I'd call in, or drop by the Vet without the dog in tow. Ask if the dog might possibly have a skin infection given the prior suspicions of mange, and ask for the antibiotics. If they say they need to see the dog, then tell them the truth- you don't have the money for another appointment, but could cover the $10 for the antibiotic. Even if you are no longer treating for mange it would be wise to ask for antibiotics. If the Vet wants to milk you for another $200, ask your friend at the ASPCA for help.
If you are still battling the mange and still on Revolution then it's important not to rub any cortisone containing salve or shampoo on the dog. That will suppress the immune system and make getting rid of the mange harder. Something like Harts oatmeal shampoo might help sooth the skin.
The benedryl can be dosed 1-2 mg/lb of dog 2X daily. Confirm dosage with a Vet.
As a dietary try you may want to consider supplementing the diet with fish oil as the Omega-3 fatty acids have a slight anti-inflamatory property. Also adding in Vitamin-E will aid in the repair of the skin. Do a search on the web for the appropriate dosage of Vitamin-E in dogs.
Dogs do not have menopause as do humans. Skin problems can range from mange, food or environmental allergies, metabolic, or auto-immune diseases.