After you've had chicken pox (and I think most people have), the virus (varicella zoster) remains dormant in your nerve tissues. I had chicken pox about 50 years ago. So did ladysolly. Your immune system keeps it under control, but later in life it can break out again as shingles (herpes zoster). The symptoms are a very irriating red rash, on one side of the body.
Ladysolly is now on antivirals for it, plus calamine to help with the irritation. Plus it's affected her social life temporarily, because it is infectious, although if you've already had chicken pox, you're probably immune. And anyway, if you already had chicken pox, you already have the virus still inside you.