I have vertical grooves in my nails as well... not all my nails, but my ring and middle fingers look and feel like a miniature wash board. they weren't always like this, but have been for some time now. Unlike yourself, my nails are on the soft side, but have improved their strength since I have been using DE. I have often wondered why my nails are like this... thanks for asking the question, and thanks to anyone who knows anything about this!!

I've always thought of them as ridges too, although they are not very pronounced. My nails have been like this for as long as I can remember... so the kidney thing is kind of scary. Any links you could share with us on that? the anemia sounds more likely in my case though as I do recall being told by the family doc to try supplementing with iron in my early teens after a blood test.

My nails have always grown very quickly though despite the vertical lines, having to clip them down weekly.(maybe that has nothing to do with it though)