I had been experiencing same condition on my left and right hands
fingernail (both thumb and index finger, rest of my
fingernails started to thicken too). They are thickening, test result is negative for fungus, the doctor told me to use Canesten. Last four months is ok, the coloring gone, but now its coming back. Then I just notice, that my nose, ears, navel and even my anus started to become itchy. I do not know if it is related to my fingernails.