Hello, i am an asian girl with fair skin and i have the vertical black lines on my fingernails and toenails. what does this mean? thanks.

Chemical reaction: Vertical lines in bot finger and toenails could be due to some chemical that was ingested.Horizontal lines are more common and again caused by a drug or something ingested.

Unsure: Black stripes down 1 nail may be subungual hematoma. Red or brown streaks may be splinter hemorrhages. Brown/black lines from nail plate to tip are often seen in people with dark skin & are normal. Subungual Melanoma can cause nail ridges & dark colors of cuticle. It most often effects the thumbs or big toes. Dark lines may be due to other illnesses. Get checked out when in doubt.