Your post keeps me thinking about how and why dogs scratch.
1] That's what dogs do.
3] They don't sweat, so skin is normally dry. I would assume then, it's like dry scalp on humans. What do we do for that condition?
4] My dogs scratch more during very dry weather. Note: Air Conditioning is a dehumidifier in the house so this may lend to extra dryness on the dogs.
5] When the weather is dry the yard chigers even get me.
6] Since orange oil is a degreaser I'd think it would remove the natural oils from the dog's skin. I need to look at cause and effect.
7] Frequent bathing with soap also removes the oils.
1] Cedar oil is not a drying agent and if used in the bath it should stay with the dog's coat and skin.
2] Cedar oil then becomes a preventative measure rather than a treatment.
3] From what I've read, the aroma of Cedar oil to an insect is the same as ammonia to a human. Therefore it should keep the insects from populating the yard.
I sure hope this is not fuzzy logic, but that's just the way I see it for now.