This is an infestation of red mange -- tiny little mites. You need to follow the vets instructions to the letter and get rid of it fast. I heard this is usually passed from mother to pup. It can affect the immune system and can sometimes be exasperated by a compromised immune system. So -- if you are looking for a premium food for support -- look for those saying they have immune system support.
I looked this up for you. It might help when choosing food:
Vitamins to Support Immune Health
If you're looking to provide your dog with additional immune support, to help stave off an illness or help in the treatment of an infection, there are some vitamins and other supplements that can help boost his immunity. Vitamins A, C, and E are essential for your dog's immune health. The minerals selenium and zinc are also helpful in the support of the canine immune system.
Some foods that contain these vitamins and nutrients include:
•Parsley
•Carrots
•Watercress
•Alfalfa
•Apples
•Bananas
•Whole Grains
•Barley
•Potatos
•Liver
•Yogurt
•Fish
Adding some of these foods to your dog's diet will make it more pleasing to his palate, as well as healthier.
Supplements that Support Canine Immunity
If you're looking for some herbal supplements to help support your dog's immune system, to keep him healthy and give him extra energy, you can try one of these:
•Atsralgus helps maintain blood sugar levels, increases vitality, and improves appetite. It could even help your dog live longer.
•Mistletoe helps prevent respiratory problems and cancer. It's also good for the circulatory system.
•Echinacea is a well known herb used for immune support. It's also good for blood pressure.
•Indian ginseng supports growth and helps cleanse and nourish the blood as well as strengthening the immune system.
•Milk thistle has been used as a liver tonic for thousands of years, and may be of great benefit to dogs with liver disease. The plant contains a compound called sylmarin, which scientists hold responsible for its beneficial effects.
•Cat's claw supports the immune system.
from:
A Guide to Dog Immune Supplements