30% mannitol cream has shown its ability to reduce the activation of the Capsaicin (TRPV1)
(Transient Receptor Potential Vanilloid 1) receptor, a likely cause of the pain of
post-herpetic neuralgia (PHN). This randomized placebo-controlled crossover study compares
PHN pain one week before, for one week on the randomly assigned mannitol versus placebo cream
and, after a three day washout, for one week on the other cream. Following this crossover
study, participants receive mannitol cream for three months. Pain levels will be checked to
assess whether continued use of this cream significantly reduces the pain levels associated
with PHN. If pain persists beyond 3 months, participants will be offered mannitol and menthol
cream for one month following which their pain levels will be checked.