Seems a few more allergy issues popping up atm - wonder if you're having a bad season over there.
Did you have a look at the itchy sansa thread
http://sheltieforums.com/threads/itchy-sansa.25949/#post-364253
What medications did you try? Antihistamines are really trial and error for dogs because many don't work. You may have to get a list of human antihistamines from your vet with dog dosages and work your way through it. Tully gets phenergan. I found the newer antihistamines don't work for Tully, and they are actually not that effective in me either.
When you did allergy testing which was it? The vet dermatologist that I saw for Deska said the blood tests for allergies are very inaccurate and doesn't do them. She does the skin scraping test instead (which requires a shaved sheltie).
I've never did get a diagnosis for Deska, although I didn't go back to the dermatologist again (she wanted us to do another food elimination trial which I'd already done twice before, and it's $300 a visit). The dermatologist did say that Tully's type of allergy, which is the straight licking of the paws type allergy is the easiest for her to treat. But I must say I never bothered because I've managed it for the last 10 years with anithistamines.
I will say regular baths with a vet quality shampoo has helped Deska - I often just wash down the effected parts rather than the whole coat. So perhaps see if bathing Chandler's feet regularly helps - at least you'll get an idea if it's actually his paws that are itching or whether his just licking the paws as a soothing thing for an overall itch.
I know when Tully first showed signs of allergies it helped to record when the paw licking and snorting was at its worst (she also used to lick furniture before I got her on antihistamines). Helped me know best time to give her an antihistamine and also if we went certain places I should wipe her paws down.
And while I remember - we had a bad year for allergies here too. I did find Tully is much worse if she lays near a doorway, whether open or not. So if the door is closed I put draft blockers across the door or I shut the door if it's open.
