There appears to be a variety of things that can trigger a GD reaction. There, apparently, is no one cause. Those interested should look at Bryan Lewis' posts on the facebook GD forum. I have not had the current shingles shot but I had the old one a long time ago. I have had GD since before 1992 when it was diagnosed by biopsy. I had shingles last summer followed by postherpetic neuralgia. Gabapentin gave me 13 years of relief from GD before it quit working. Took it again for the postherpetic neuralgia and it helped. Still itching from the GD although I think NB UVB light treatments helped a little and Eucerin Itch Relief along with Hydroxyzine at night helps too.