you made a comment about weather changes.... this was something that I just spoke with a few other people about, on a website and in my store.

In winter we humans tend to turn up our heaters for what's comfy for us, but, we don't wear a fur coat. What's comfy for us might be too hot and too dry for our furry companions.
The add dryness and heat can dry out their fur and skin. Causing itchiness, dry and flaky skin. Often times this is mis-diagnosed as an allergy.

You can try adding a humidifer to the home, turning the heat down when you're not home or a sleep. There are a variety of skin and coat supplements to add to the dogs diet, lipiderm, missing link, etc... basically you're looking for a supplement high id omega 3 & 6 and/or fish oils.