Re- vaccines, my own experience, fwiw: I started having itchy skin problems on my face about 3 years ago (diagnosed as rosacea), before I got the Shingrix vaccine. The problems gradually progressed downward after I got the vaccine, down my neck and onto my shoulders, manifesting differently on different types of skin – I can't be sure whether there was a connection among the different kinds of itchy disorders, or with the vaccine. Once it reached my shoulders, it was there diagnosed as GD and confirmed with a punch biopsy.

I have to note that most people seem to develop GD after they've gotten older, which happens to be when the vaccine is recommended; so although I'm open to the possibility that there's a connection, it also seems to me that the timing of the two could be coincidental.

That said... I had the chickenpox vaccine when I was an infant and have the scar in my left shoulder, and I too eventually noticed that the scar itched just like a GD bump – in fact, for quite I while, I felt an itchy, small bump there and assumed it WAS a GD bump, until finally I actually looked at it and realized there was no perceptible GD bump there or near it. So that got me wondering about some kind of viral connection, and I asked about it here; but you're the first one I've seen so far to also mention an itchy vaccine scar.

Also fwiw, I have not been able to confirm any cilantro-based benefit in my case.

I've still got the GD – it progressed slowly down my body and my efforts to control it now cover my arms as well as my chest and back– but it's not as bad. Seems to be slightly helped by cortisone cream, antibiotic cream, and/or adalpene gel. At the moment I'm suffering more from what I believe to be atopic dermatitis, mainly in my armpits and inner elbows – again, however, this seemed to be part of the gradual progression down my body.