Actually it sounds like hives to me. It is common for hives to start around the hairline/neck area. You may be having an allergic reaction to something you ate, or any medication you took recently? If the benadryl is working, continue to take it as directed. Don't use a topical benadryl cream, instead use a cortisone cream. Use creams as directed to prevent a chemical burn and don't mix the creams.
Shingles is actually a mutation of the chicken pox virus, and if you had the chicken pox the virus can remain inactive in your system only to flare up later in life as shingles. Shingles usually effects older adults so it's not unheard of. If it is shingles your doctor can give you a prescription for an anti-viral medication like Valtrex.
http://www.shinglesinfo.com/index.html?WT.srch=1&WT.m...
I have super sensitive skin and am allergic to some medications, so I have dealt with hives myself. I also have family members who have chronic shingles.
Good luck!