thanks. just did it...had it on for 20 minutes and had to look under a bright light and have a tiny bit!. Put it on three fingers. Do you think leaving it on for 10 more minutes would make a big difference? I did have a negative skin punch so I at this point (since I have had this pain for so long) am thinking I do not have SFN even though I have all of the symptoms! Still waiting for my dr to come back from vacation though but it seems that the punch biospy is really the gold standard and I can't imagine getting a diagnosis with a negative one, although I'd loved to know why my feet burn and why my bladder is a MESS!!!