How often are you bathing him? He may have lost a lot of oil in his skin due to over bathing. Normally, a dog is only bathed when it needs it, no more. It's possible it may be the Eukancrapa that you're feeding him, but it's more likely the shampoo. Switch him over to a good quality food, such as Nutro, Solid Gold, or Wellness, and see how his skin does. If he's still dry and flakey, try adding a little bit of cod liver oil (just a bit!) to his food, once per day. The "little" bit of extra oil should help his skin recover.
Other than that, try not to bathe him unless he rolls in something, or gets really filthy.
That's the best I can come up with at the moment.
I'm firm - but fair. Mind the rules and enjoy your stay.
According to the Humane Society of the United States:
There are an estimated 3-4 million dogs and cats euthanized each year in the US alone! PLEASE - spay and/or neuter your pets!