For the longest time I've had a light black or greyish vertical line down one of my nails and then all of a sudden two more have popped up on other nails. Curious to know if anyone else has had this, and what causes it?
Have you smashed your finger at some point? My guess is that it is blood - and usually when blood shows up under a nail it is due to an injury to the finger. (It could have happened a long time ago and is only now showing up.) Otherwise, maybe it is a circulation issue. ALL of my nails take on a bluish tinge when my iron is low or when I'm very cold.
I had this on one of my toes when I was running a lot. I was so scared and after talking to my doctor I learned that it was from smashing my toe. I thought it was a circulation issue. It went away after the nail grew out, but it did take some time.
You probably smashed them really hard somewhere. Get it checked out. Once my daughter threw s whole liter bottle of water from her crib on to my hand on the floor. It hurt so terribly hard I started to cry. It firmed a greyish black spit on my nail that took 6 months to grow out. It is probably that. It could belinear melanonychia.
I guess the other posters are right, it might be a circulation issue or a blood clot. I also had a white spot appear out of the blue in my nail before but it disappeared over time too. I suspect it's because I had some sort of nutrient deficiency.
