So Theo has dry skin. Itch, itch, itch. Itch, itch, itch. It's driving him (and me) crazy this winter. A few facts:
--We live in a temperate climate, so we rarely have the heat on (so it's not dry hot air from the register).
--He itches a lot (everywhere) and fusses at his paw pads and tail, but not to the point of developing hot spots.
--His skin does not look red or like eczema; it's just dry and flaky (just like mine, actually).
--His food has no wheat or corn. (We feed Nature's Variety.)
--We took him off all treats that might have wheat and corn in it, with no effect.
--We tried Benadryl (75 mgs./day for two weeks; he weighs 75 lbs.), with no effect.
--He gets a salmon oil supplement daily. His coat is great--shiny and harsh and oily and repels water well.
I'm pretty sure his skin is just dry. He does swim in the Bay almost daily, so the salt water (or who knows what else is in the water) could be irritating his skin. But I would hate to deny him that enormous pleasure. We do try to rinse him thoroughly afterward.
It's been a few weeks since we've been above freezing, and more importantly the dew point has been extremely low producing humidities in the 15-25% range. When it gets like this (then throw in fires in the fireplace and the heater) I've found that there is no nutritional cure for Jes's or my dry skin. The only thing that helps is a humidifier...at least that's the only thing I've found.
The omega-3s and extra protein helps, but not when the air gets this dry.
Have you considered the possibility of his itching being due to something environmental? grasses can be a common irritant.
This may be pretty obvious, but what about fleas? I would also say mites, but usually the skin is red and inflamed with that.
What about treating him with a herbal shampoo (got a holistic vet near you?) and keeping him out of the bay for a week or so to see if it clears up? adding a teaspoon of fat (regular olive oil is fine) to his diet might also help.
I didn't run my humidifier for a few nights and started noticing even my own skin was itchy. I keep one going in the bedroom all night. I also think I need to get one for downstairs as I've noticed a lot of the blankets on the furniture have static electricity in them!
I also use Nupro ... it's worked pretty good for Dutch.