These are often very helpful if done properly. First wet the fur well, then shampoo the dog creating a good lather and let that sit on the dog for 10-15 minutes. Rinse well...and then rinse again! Soap left on the skin can cause the type irritation you describe (flaky, itchy redness)so its important to rinse well, twice. Usually they are given twice a week for couple weeks to improve a 'general itchiness/light irritation'.
I use either Malaseb shampoo or Chlorhexiderm 4% shampoo...both have antibacterial/antifungal qualities.
