Just to be sure, I would still see a dermatologist unless this clears up very quickly.
Just because you didn't change brands, it doesn't mean the brand itself didn't change the formula or add something. Anything that says "New and Improved" or simply seems different when you use it can trigger a rash.
Scabies would appear between fingers, elbows, other warm parts... and itch mostly at night.
Ask me how I know... had to fly back to France from Canada with the worst itch. My mom took one look at me and sent me to the dermatologist. yep, she was right. Scabies. So I don't think that is what you have!