What causes them? I have a wavy set of horizontal ridges on my right thumbnail and I can’t figure out what’s caused it. I don’t remember hitting it against anything, closing a door on it, bad nutrition, or anything like that. And what really puzzles me is that it’s just on my right thumb; none of my other fingers have anything like that.
Vitamin B deficiencies … even if your intake is adequate you may not be metabolizing them properly … which could be due to Vitamin E deficiencies … are you mildly anemic? … try a Vitamin E supplement, see if these conditions go away after a year or two … not a lot, just a little … and cut back on processed foods … these are notorious for lacking Vitamin E and some of the B Vitamins …
Your nails basically extrude from the matrix, so any persistent irregularity in the matrix is going to cause ridges. It’s analogous to spreading mortar with a trowel, in that any irregularity in the trowel edge will result in ridges being generated in the mortar.
Crosswise ridges might be Beau’s lines. Or Mees’ lines. Or Muehrche’s nails. Or something else. If you are concerned and/or you’re having other symptoms, you might want to see your doctor (or call a nurse hotline for a quick phone consult, if you have that resource available to you).
I have spots of mild eczema on the skin at the sides of each thimbnail and one middle finger. Sometimes when I get stressed out, the eczema flares up, and I end up with ridges as the nail grows out. None of my other fingers get ridges.
The great majority of nail abnormalities are due to random variations in the nail matrix, and do not represent any underlying disease, deficiency, or threat to health or life. The likelihood of diagnosing a previously undetected illness or nutritional lack based on investigating a nail change is quite small, though certainly not zero.
To clarify: this is only true of ridges that are horizontal (across the nail). Vertical ridges (along the nail) are not indicative of vitamin deficiencies, just age.