We all have it stored in our bodies if we had chicken pox. The question is why does it resurface. Just getting older with lowered immunity is the main cause. Or being under stress or illness that lowers immunity. I have also read that a back injury can bring it on as it is stored in the spine? Not long before my bout of Shingles years ago I had a very dramatic chiropractic adjustment to my lower back. (I do not see a chiropractor anymore and that was when I was younger). But the main thing seems to be immunity as the issue.