Aaah... "P" the pain messenger. This is what Zostrix is supposed to gradually lower... I did not even have an open cut or a scratch and I thought I was in the fires of hell when I tried it...

This from a website selling it:

Zostrix is not only effective; it’s also safe. Zostrix has no known systemic side effects or drug interactions. This means that you can feel comfortable knowing Zostrix will not interfere with the oral medications that you may take for arthritis or other conditions.
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HOW DOES ZOSTRIX STOP THE PAIN?
Zostrix works with your body's chemistry to lower your level of Substance P, the body's "pain messenger." When Substance P is reduced, so is the pain. By using Zostrix regularly, 3 to 4 times a day, capsaicin builds up, Substance P fades, and so does your pain.

Probably the reason they sell a lot of it is that everybody tries it "once."

Cathie