My DR prescribed some liquid stuff, (I don't have the bottle here, but it was Ciplorox or something like that). Put it on the nail and the adjacent ones (it can spread), every night. After the bottle ran out, I waited. Stuff came back. Next time I saw the DR, he said lets try it again. He said if the second go-around didn't work, then we could do the pills-internal stuff, but he'd prefer not to. Second time, it worked! Killed the stuff. The other things to do are change your socks a few times a day and even just slip off your shoes at work a few times a day and let the dogs air out.