It does not fail it can be cold or hot but my feet constantly sweat. My feet are so sensitive that the slightest touch makes them even sweatier. They're a little dirty but they are absolutely glistening. It looks like they were freshly licked and the saliva is still fresh. Watch me wiggle my toes and talk about how sweaty they are. (I'm still figuring out my camera so it will go in and out of focus a couple of times but not for long and I make sure to get my sweaty feet back in focus)