What you describe sounds like hives. Hives are welts which come and go and itch. Despite their reputation, hives are rarely allergic in nature (unless the association is obvious, which it usually isn't, as in your case.)
Does that mean that hives can "just come"? Yes. They also "just go."
To tide yourself over, you can while wiaitng for an appointment:
1) Take a photo of the welts in all their splendor.
2) Apply Sarna lotion (OTC) as needed for itch.
4) Take Benadryl 25 mg or chlortrimeton 4mg at bedtime (OTC-may cause drowsiness.)
Don't be shocked if the hives are long gone before the doctor gets around to seeing you.
Best.
Dr. Rockoff