I began taking 2 drops of Lugol's iodine daily for brittle nails. Within two weeks my nails are unbelievably strong and hard. Also, I injured one nail over thirty years ago below the growth line. Every time this nail begins to grow it, it would crack vertically. I was told there was no remedy. I now have a nail growing on that finger!! No explanation other than the iodine. I am a believer!