Shingles are the herpes zoster virus that lies dormant in your nerves after you have chickenpox. You must first have chickenpox at some time in your life to get them. For some unknown reason they resurface, following the nerve causing blister like rash with some itching but often with pain. It can last for several weeks.
People who are elderly or immunocompromised can get horrible, total body episodes of them and would be hospitalized and isolated. Most people get them around one side or on the side of their face.
The others are right, it occurs on one side of the body and usually does not spread. Notice the "usually".
In case you all have not figured it out yet, medicine is really a lot of guessing at times. If there is a major episode and they really need to know they could probably do some scrapings and send it off to the lab. They usually don't do those for ordinary cases. Not that tuffcookie is by any means ordinary.
The best advice I would give is keep it covered, wash your hands. Keep your doctor aprised of the progress. Use calamine lotion or soothing baths of aveno or, put old fashioned oatmeal in the toe of a knee high stocking and soak in a tub with this in it. Instant oatmeal bath. Take benedryl if it is itching and watch for any signs of infection.
Tuffcookie, if you are not having pain of any kind, I would tend to think poison ivy or another contact dermatitis. I have never spoken to anyone that did not complain of pain with shingles.
I hope you get better fast.