Dogs need Omega 3 and 6 fatty acids. Just feeding dry dog food is the worst thing you could do. I put cod liver oil in my dogs food each day. ( I cook for them also) Also make sure you use a very gentle shampoo and rinse, rinse and rinse again. Use 1 tablespoon of distilled white vinegar to 1 pint of warm water for the final rinse. It takes out any remaining soap and is a natural flea repellent. The best is Dr. Bronners liquid castile soap. It's gentle enough to use every day and gentle enough for a newborn baby. You can also bath and shampoo in it yourself. He has some with eucalyptus tea tree or Lavandin& Lavender. These scents keep fleas off too. He has a new line out called Sun Dog's Magic that I'm anxious to try. Right now I am switching back and forth from #1 All Systems to the liquid castile soapl.
http://www.drbronner.com/drb_sai_liquids.html