[shelties mom]

This sound to be a yeast problem, no. 1 thing to do is to address the diet, preferrably an anti-inflammatory raw diet with no grains. Adding a probiotic supplement will help since antibiotics destroy all good along with the bad bacteria, so these drugs often make a bad situation worse.

http://healthypets.mercola.com/sites/healthypets/archive/2011/05/03/eating-these-foods-can-make-your-dog-itch-like-crazy.aspx

Be sure not to over-vaccinate or over-medicate.

http://healthypets.mercola.com/sites/healthypets/archive/2010/08/17/stop-using-pet-steroids-until-you-read-these-disturbing-truths.aspx
http://healthypets.mercola.com/sites/healthypets/archive/2009/12/23/environmental-allergies-and-your-pet.aspx

Use natural flea control products:
http://healthypets.mercola.com/sites/healthypets/archive/2010/03/31/dangers-of-flea-and-tick-problems.aspx

Have you tried this product for his ears?