puppy with demodectic mange

Question
Hello, I have a 13 week old male puppy who has been diagnosed with demodectic mange. He has two small spots on one of his front legs and one spot on one of his back legs. I have been given a topical treatment to hopefully prevent it from spreading and requiring dipping. I put Goodwinol ointment on his spots once daily. The vet was not sure if it was localized of generalized but I have been doing some research and it says less than 4 spots is usally localized which, from what I can gather, is the better of the two. My worry is that it will spread and he will require dipping, which I am not sure if I can afford. I am having trouble just keeping up with his shots, flea, and heartworm treatments. I feed him Science Diet and have read alot about the immune system being compromised with a low quality food, is this a good food to be feeding a puppy with demodectic mange? I feed him Science Diet puppy small bite formula. Is there another food you would recommend or a supplement you would recommend to help his immune system hopefully grow out of the demodectic mange? Any help would be great. I try my best to give him the best care I can but it is starting to get taxing and I do not want to come to a turning point where I have to choose so I want to prevent things from happening as best as I can. Please let me know any help you might have.

Answer
Any stress can make the immune system weaken, including a poor diet. Science diet is an excellent food.  Demodectic mange, in my opinion is always generalized.  We dip all pups for mange regardless of how many spots thay have.  That's just where the hair fell out. Another option is ivermectin given for 30-45 days.  That is available from your vet or from a feed store.  Check with your vet before doing anything else.