I've been long distance hiking now for a few years. In the early years I went through my blister period and then overcame the problem but in the latter part of 2018 I experenced what was for me, a new problem. I lost three toenails! It didn't happen suddenly, it just crept up on me from August to December. My rucksack weight hadn't changed but I did buy new socks and a new pair of boots which I felt were comfortable for most of the time I was hiking. I had two days of wet feet when they were not comfortable and it was then that I noticed that one toenail had started to go black. Gradually two others went black but it was some weeks later. Then over the Christmas and New Year period they came off. All is OK now, the new nails have grown back.